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Home , Asterion (anatomy), Craniometry, Lip, Mental protuberance, Nasal bone

Edinburgh Medical Journal

June 1927

THE OF THE MONGOLIAN IMBECILE.

By DAVID M. GREIG, C.M., F.R.C.S.E., F.R.S.E., Conservator, Royal College of Surgeons' Museum, Edinburgh.

(Continued from p. 274)

How closely alike these are to each other, super- imposition of their outlines conclusively demonstrates whether the orientation be lateral (Fig. 8) or facial (Fig. 7). Nor is there any reason to believe that increased age would have altered their main characteristics. Such measurements as Dr Fraser gives of the skull of his female mongolian imbecile I have added to the appended Table (Table I), and obviously

TABLE I.

Measureme7its of the mongolia,7i Skulls.

Dr. J. Fraser's 16. 14. 5. Case, Sex and Age P., F., F., F., 40.

Circumference 457 455 420 437 Length 153 156 142 146 Breadth 129 134 123 131 84.31 85-89 86-59 89.72 Height 116 112 108 Altitudinal index 75-Si 71.79 76-05 Basinasal length 76 82 76 Basialveolar length 75 74 72 Gnathic index 98-68 90-24 94-73 Nasal height 33 35 30 35 Nasal width 19 19 19 22 Nasal index. 57-27 54-28 63-33 60-84 Orbital height 32 34 32 35 Orbital width 34 3i 32 35 Orbital index 94-n 91.17 100 100 Ophryo-mental length 97 100 9i Bizygomatic width 103 108 95 107 Total facial index. 94-17 92-59 95-76 Ophryo-alveolar length 99 59 56 Superior facial index 96-11 54-63 58-93 Cranial capacity (c.c.) 1070 1030 845 Weight (grams.) . 368-55 297-67 283-5 454-59

VOL. XXXIV. NO. VI. 32 1 David M. Greig there is little to choose between my skulls and his though his patient was 40 years at death while the oldest of mine was only 16 years. The attainment of adult life by mongols is exceptional, old age probably unknown. Sir Arthur Mitchell gives the highest age at death among his 54 mongols as 43 years.

Fig. 7.?Superimposed millimetre-scale drawings of skulls of three female mongolian imbeciles. The dotted line is that of Skull I, the interrupted line that of Skull II, and the continuous line that of Skull III.

The are skulls brachycephalic, hypsocephalic and ortho- gnathic, platyrhine and magaseme, and in all the orbital fissures are large. A flattening of the and of the occiput, such as has been described, so that their planes are parallel,' is not found in these macerated skulls. It -seems as if the difference made by the soft parts had been under-estimated, and 322 Skull of the Mongolian Imbecile

the filling up by the nuchal muscles and the fleshiness over the zygomata had not been appreciated. In Skull I there is a slight left plagiocephaly, and curiously enough a similar deformity was noted by Fraser in his skull

Fig. 8.?Superimposed millimetre-scale drawings of skulls of three female mongolian imbeciles. The dotted line is that of Skull I, the interrupted line that of Skull II, and the continuous line that of Skull III. already referred to, but the condition is of little moment unless the details of birth and infancy are known (cf. Greig0). Skulls II and III are symmetrical, and all are small, globular and light. The are smooth, ill marked with fascial and muscular attachments, and as regards their cranial capacity all the skulls are decidedly microcephalic. Their orthocephaly 323 David M. Greig or hypsocephaly provides a feature in their altitudinal index which removes them absolutely from the category of the true microcephalic imbecile and small-headed idiot. Thus in the microcephalic the ratio of face to cranium is obviously disproportionate to the disadvantage of the cranium, whereas in the mongolian imbecile a mere glance is sufficient to recognise in the general smallness of the skull a proportion- ately large cranial capacity. In this is expressed by the preponderance of the facial indices in the microcephalic. In order to compare the points of difference between the mongol and the microcephalic skulls, I have taken three skulls of microcephalic imbeciles of nearly the same age as the mongol skulls I am dealing with, and these yield the measurements given in Table II. The mongols in question were females aged 16, 14, and 5 years respectively, the micro- cephalic skulls I have chosen for comparison are those of females aged 19 and 16, and that of a male aged 9 years. None of the females had shown signs of puberty, a physiological occurrence which is delayed in mongols and microcephalics alike. The points of difference may be observed by comparing Table I with Table II, but a more striking comparison may

TABLE II. Measurements of three microcephalic Skulls.

Sex and Age. P., 19. F., 16. M., 9.

Circumference . 365 400 360 Length 132 145 128 Breadth ]OI 113 99 index . Cephalic 76-51 77-93 77-34 Height i?5 104 94 Altitudinal index 79-35 71.72 73-43 Basinasal length 90 81 Basialveolar 90 length 92 92 74 Gnathic index 102-2 2 102-22 Nasal 91-35 height 39 41 35 Nasal width 20 21 20 Nasal index 51-27 51-21 57 Orbital . height 28 34 3i Orbital width 32 37 3i Orbital index 87-5 91-89 100 Ophryo-mental length 120 127 105 width Bizygomatic 98 103 95 Total facial index 122-44 123-9 110-52 Ophryo-alveolar length 88 90 78 facial index . Superior 89-79 87-37 82-1 Cranial capacity (c.c.) 690 530 410 Weight (grams.) 354-37 340-2 240-97

324 Skull of the Mongolian Imbecile

be made by taking the average measurements of the three typical mongolian skulls and placing them in juxtaposition with the three typical microcephalic skulls as I have done in Table III.

TABLE III.

Comparing the Average Measurements of the mongolian Skulls with those of the microcephalic Skulls.

Age Mongolian, Microcephalic, 12. 15.

Circumference 444 375 Length I50 135 Breadth 129 104 Cephalic index . 85-66 77.26 Height 112 101 Altitudinal index 87-55 74-83 Basinasal length. 78 87 Basialveolar length 74 86 Gnathic index 94-55 98-59 Nasal height 33 38 Nasal width 19 20 Nasal index 58-29 53-i6 Orbital height 33 3i Orbital width 32 33 Orbital index 95-09 93-13 Ophryo-mental length 96 117 Bizygomatic width 102 99 Total facial index 94-17 118-95 Ophryo-alveolar length 68 85 Superior facial index . 69-92 86-42 Cranial capacity (c.c.) 982 543 Weight (grams.). 3i6-57 311-85

This shows that the mongol's skull is brachycephalic, that of the microcephale is mesaticephalic; the mongol is hypso- cephalic, the microcephale is orthocephalic; the mongol is orthognathic, the microcephale is mesognathic. There is little to choose between their nasal and orbital indices, but in the total facial index, as in the superior facial index, the preponder- ance is decidedly with the microcephalic. The great zygomatic breadth is in proportion to the brachycephaly. Though both are microcephalic as regards cranial capacity, that of the mongol is nearly double that of the microcephale. The three skulls mongol have certain features in common, and several indicating a delay in the completion of the develop- ment, delay which Dr John Fraser's skull shows to persist throughout life, It might be expected that as the frontal and parietal vol. xxxiv. no. vi. 325 z 2 David M. Greig tuberosities are so frequently prominent in infancy and child- hood they would be in evidence in mongols, but none of these skulls show any of the tuberosities well-marked, not even the frontal. In the youngest of the skulls there is more fullness just above the ophryon, and this in association with a complete metopic suture. It is not a carina, but a mere fullness, such as is still so often erroneously ascribed to premature synostosis of the metopic suture. That suture is present in its entirety in two of these skulls aged 5 and 14 years, but is practically obliterated in that of the girl aged 16 years. As with the frontal tuberosities so with the super- ciliary arches, they are not in evidence. Le Double8 has noted that absence of the frontal sinuses is more common in skulls in which the metopic suture persists than in those in which it has undergone obliteration. Indeed, in the mongolian skulls, there is a lack of development of all the accessory respiratory sinuses, and this gives to the maxillary bodies an appearance of insignificance. As the flat, soft snub-nose is so characteristic in the mongol during life, it is not surprising to find the nasal bones offering peculiarities. In Skull I the nasal bones are completely absent, in Skull II the nose is neither flat nor broad but well formed though the nasal bones are somewhat narrow, and in Skull III only the right is present and though of good size is almost vertical in position. The nasal bones were absent from the skull described by Dr John Fraser. Many cases of absence of the nasal bones are on record in association with gross facial deformity, but these have 110 relation to the condition in mongols' skulls. Manouvrier9 has pointed out that when the nasal bones are absent they may be replaced by the frontal or by the frontal processes of the maxillae, a condition which was present though only to a slight extent in the skull of an Admiralty Islander described by Turner.10 Skulls illustrating these various conditions have been figured and described by Wahby.11 In the skull of the mongolian imbecile, however, no attempt is made to replace the nasal bones. That they have been represented by membrane there is no question, but the membrane has never become ossified. The adjacent bones are normal and have not undergone compensatory modification. In Skull III, where only the right nasal is present, it articulates at its base with the right half of the frontal only. Though for some 326 Skull of the Mongolian Imbecile

distance it articulates with the frontal process of the left its distal extremity does not complete the nasal bridge. A small triangular space is left which was doubtless occupied by . Evidently the growth of the frontal processes of the maxillae has participated in the disturbance, for in Skull I each presents a partial vertical division and in Skull III they are grooved vertically and are very broad. In Skull II, in which the nasal bones are normal, the frontal processes are correspondingly well formed. In Skull I there is a small left sutural bone and in Skull III the frontonasal suture is horizontal. In all three the nasal aperture is slightly asymmetrical, and in Skull III the inferior margin of the aperture is horizontal and the nasal spine short and blunt. Within the the perpendicular plate of the ethmoid is very short in Skull I, short in Skull II, and apparently altogether undeveloped or unossified in Skull III. It would probably not be incorrect to say that in the mongol the nasal apertures have normal breadth but are diminished in height. In Skull I the has a right lateral deviation. The small size of the maxillary body in Skulls I and II has been already referred to. It is not so evident in the youngest of the three skulls. The most striking features in the maxillae is the want of development of the alveolar processes, especially anteriorly. An osteoclastic without some corresponding osteo- blastic activity is inconceivable, especially if a septic process is presumed as a casual adjunct. All writers on the physical features of the mongol refer to the swollen and inflamed , and some mention an hypertrophy of the alveolar processes, but these skulls fail to show any such bone-cell reaction. In Skull III the anterior aspect of the maxillae is remark- ably flat, recalling Sutherland's description12 that the face " (and occiput) seem actually depressed, as if some force had driven them inwards." In none of my skulls does this hold good as regards the occiput, but it is very striking in the norma facialis of Skull III, in which it is associated with a flattened almost vertical nasal bridge. The premaxilla is a later embryonic structure to appear than the maxilla and helps to form the nasal process. Fawcett25 quotes Callender as suggesting that the early union of the body of the premaxilla with the outer alveolar wall of the maxilla is due to a maxillary clip coming forward in front of the premaxilla, and so shutting it out from the face. The condition present in mongol skulls is such as to 327 David M. Greig suggest that this process from the maxillae has not formed, and that the facial aspect of the alveolar portion of the premaxilla has therefore remained defective. It is not a question of want of the of the maxilla depending on inadequate development of the teeth, because the defect noted in the pre- maxillary area is not found in the maxillae. Even though the teeth may be distorted or not well developed, the upper incisors cannot be stigmatised as more at fault than the other teeth in the dental arch, and the defect is so localised that it points to a primary disturbance of the premaxillary alveolar growth, and not a general and secondary defect. Another point of difference between these skulls and the usual accepted description of the mongol's peculiarities is that the is well formed and flat, though according to Muir14 palatal deformity was found in 67 per cent, of mongolian imbeciles. Nor do these skulls show the alveolar hypertrophy which Brushfield lu states is nearly always found after the sixth year. In Skulls II and III the anteroposterior measurement behind the transverse palatal suture is less than normal, but this would not be recognisable during life. Since there is no alveolar hypertrophy, and the palate is neither narrow nor high, it is probable that the swelling and thickness of the inflamed gums have induced erroneous deductions and inflammatory gingival reaction has been mistaken for alveolar overgrowth. Before considering the teeth in either it will be convenient to deal first with the . The mandibular rami are short and well-formed. The angle is by no means foetal, that of Skull I being 140?, of Skull II 1350, and of Skull III ioo?. This is a little surprising, especially as regards Skull III, the youngest skull. The body of the mandible is substantial, and each presents a lateral bulge at its junction with the ramus, giving a breadth and fullness to that part of the face which, apart from the palpebral obliquity, is probably the most striking feature. It is this that gives the character- istic squareness to the mongol's face, while the diminution in the normal obtuseness of the angle helps to emphasise the flatness of the facial aspect. The mandible is of unusual the thickness, maximum in Skull I being 10 mm., and in Skulls II and III 13 mm. The mental foramina are small and seem nearer the alveolar process than usual, while in each the of skulls the anterior half of the mandible has a slight 328 Skull of the Mongolian Imbecile upward inclination enough to raise it above the level of the lower border of the mandibular body. The lower border in all is thick and rounded and the is distinct. Sutherland12 stated that the mandible in mongols projected forward, and from this the upper was sucked in by the lower. My skulls do not show that feature, but shortening of the upper alveolar process or flattening of that part of the maxillae might bring about such displacement of the . The smallness of the teeth and the "squareness" of the broad mandible would also predispose to protrusion of the lower lip. According to Ballantyne13 the mandible in the full-time foetus is small, its angle is obtuse (1750), and it lies on a plane posterior to the maxillae. In the mongol the mandible is relatively large and massive, its angle is far less obtuse than in the foetus, and its upper margin is certainly not behind the alveolar margin of the maxillae. It is not the shape of the mandible that gives the prominence of the in the infant but the suctorial pads of fat which lie on the buccinator and masseter muscles. In the mongol it is the bone itself which is broad, and the squareness is accentuated by the great interzygomatic breadth. The breadth of the mandible, which is probably a character- istic of the mongol's skull, appears to be the direct outcome of its environment and of muscular action. The lateral pressure exercised by the large soft of the mongol cannot be disregarded in this connection. The pressure of the normal tongue, according to Wallace,35 acts primarily on the teeth, but secondarily through them on the alveolar process and on the bone. There is no doubt that the tongue modifies the shape of the mandible, though perhaps its action is not so primarily on the dental arch as Wallace suggests. That it is a factor in the mongol there can be no doubt. There is another well-known feature of the mongolian imbecile which seems to me never to have been sufficiently taken into account in the moulding of the mandible; I refer " to that condition known as fissured or scrotal" tongue. This is well known to be extremely common in mongols, though not universal. I cannot, from my own more limited experience, cite such exceptional cases, though certainly the fissuring is much less pronounced in some cases than in others, but the late Dr John Thomson assured me he had seen typical mongol children in whom fissuring of the tongue did not exist. If 329 David M. Greig this condition of the tongue is due, as in all probability it is, to " the habit of tongue-sucking," the act of sucking which pressing the distal portion of the tongue against the central and anterior part of the palate would tend to broaden somewhat the proximal or posterior portion of the tongue which would be spread out by muscular action and so would exercise centrifugal pressure on the mandibular body and especially on its posterior part. Fissuring of the tongue is not congenital, but is acquired in ?infancy and exaggerated during early childhood. It is not confined to mongolian imbeciles but occurs in quite mentally- efficient persons. I have seen several cases of this lingual affection in healthy adolescents, and I do not remember a single case in which the mandible was not unusually broad posteriorly with corresponding increase in breadth of the lower part of the face as is found in mongols. The study of these skulls suggests the obvious explanation. The main defect is want of growth of the facial bones, chiefly of the maxillae and of the alveolar processes anteriorly. With this failure of development the mandibular body has not been pushed downwards as it normally should be, hence the ramus stands more vertical to the body. But further, as the most defective development is in the premaxillary region, the anterior part of the mandible has been left without its natural countercheck and so has acquired an upward displace- ment. This explains the upward tilt of the anterior part of the mandibular body as observed when that bone is laid on a plane surface. The mandible itself does not participate in the defective development, and growth, being uncalled for in other directions, may be some reason for its unusual breadth and thickness. The teeth in mongols, Dr John Thomson16 writes, are generally small, and tend to become yellow and to decay early. Comby17 and others have noted delayed eruption, and Hall18 has called attention to the fact that the permanent is not so irregular as the milk dentition. Though my skulls do not bear this out. In view of the considerable variation in the order and date of eruption of the teeth in normal children it is difficult to specify any aberration as distinctive of the dentition of mongols. But doubtless diversity is more frequent and greater in mongols than in normal individuals. It might be stated that in the mongolian imbecile there is an irregularity of as a the teeth whole, and frequently an irregularity of 33? Skull of the Mongolian Imbecile individual teeth more pronounced in the upper than in the lower series and more definite in the anterior than in the posterior teeth. In the description of the skulls I have detailed the condition of the teeth in each of the three individuals, and to facilitate comparison I summarise the main factors in the following table:?

Maxilla.

Skull No. Right Central Incisor. . . . Projects forwards mesially. Short root. II. ... Enamel defective. Edge notched. Root short. Not fully erupted. . . . Milk. Well formed. Carious.

Left Central Incisor.

. . . Dilaceration. Cutting edge notched. Short root.

. . . Carious. Root short.

. . . Milk. Well formed. Carious.

Right Lateral Incisor.

. . . Congenitally absent.

. . . Still embedded in bone.

. . . Milk. Well formed. Carious.

Left Lateral Incisor.

. . . Crowded. Obtuse. Rounded.

. . . Congenitally absent.

. . . Milk. Well formed. Carious.

. . . Sii'per7iuvierary teeth between milk canines and permanent central incisors.

Right Canine.

. . . Just erupting. Projects mesially. Milk canine still present. . . . Milk present. Has a hyperplastic spot. Permanent, just. erupting. . . . Milk. Substantial.

Ltft Canine.

. . . Normal but rotated.

. . . Milk present. Permanent, just erupting.

. . . Milk. Substantial.

Right First Premolar.

. . . Projects mesially.

. . . Normal. 331 David M. Greig

M AXILLAE?co?itinued. Skull No. Right Second Premolar.

I. ... Rotated.

II. ... Normal. Left First Premolar. I. ... Normal.

II. ... Normal. Left Second Premolar. I. ... Normal. II. ... Displaced. Right First Molar. I. ... Absent. Probably destroyed by caries. II. ... Enamel striated and yellow. III. ... Milk. Normal. Permanent in crypt. Right Second Molar. I. ... Absent. Accidentally lost. II. ... Just erupting. III. . . . Milk. Normal.

Left First Molar. I. ... Carious.

II. ... Enamel striated and yellow.

III. . . . Milk. Normal. Permanent in crypt.

Left Second Molar. I. ... Absent. Accidentally lost. II. ... Just erupting. III. . . . Milk. Normal.

Mandible. Right Central Incisor. I. ... Absent. ? Destroyed by caries. II. ... Absent. ? Congenitally. HI. . . . Permanent erupting. Left Central Incisor. I. ... Absent. ? Destroyed by caries. II. ... Absent. ? Congenitally. III. ... Permanent erupting. Right Lateral Incisor. I. ... Absent. ? Destroyed by caries. II. ... Normal. Short root. III. . . . Milk absent. ?Congenitally. Permanent in bone. Left Lateral Incisor. I. ... Mesial inclination. Slender crown.

II. ... Normal. Short root.

III. . . . Milk. Normal. Carious. Permanent in bone. 332 Skull of the Mongolian Imbecile

Mandible?cojitinued.

Skull No. Right Canine.

I. ... Lateral inclination.

II. ... Normal.

III. . . . Milk. Carious.

Left Ca?iine.

I. ... Absent. Milk present.

II. . . . Normal.

III. . . . Milk. Carious.

Right First Premolar.

I. ... Normal.

II. ... Normal.

Right Second Premolar.

I. ... Absent. Accidentally lost.

II. ... Normal. Rotated.

Left First Premolar.

I. ... Absent. Accidentally lost. II. ... Not erupted.

Left Secotid Premolar. I. ... Compressed mesiolaterally and rotated. II. ... Not erupted.

Right First Molar.

I. ... Absent. Caries or extraction. II. ... Slightly carious. III. . . . Milk. Practically normal. Carious. Permanent in crypt.

Right Second Molar. I. ... Tilted mesially. II. . . . Not erupted. III. . . . Milk. Practically normal.

Left First Molar. I. ... Absent (caries or extraction). II. ... Carious. III. . . . Milk. Carious. Permanent in crypt.

Left Second Molar. I. ... Slopes mesially. II. ... Erupting. Rotated. III. . . . Milk. Enamel defective. Carious. 333 David M. Greig In the youngest of the three skulls ossification at the is uncompleted. In Skull I the coronal suture is oblique in accordance with the plagiocephaly present. In Skulls I and II there are sutural bones in the as well as at each . The parietal foramina, normal in Skull II, are unusually large in Skull I and only the right is present in Skull III. In Skulls I and III an arcuate suture is present in relation to these foramina. In Skull I the right external acoustic meatus is slit-like and it and the right mastoid process are smaller than the left. In all three skulls there is some indication of division between the supra-occipital and interparietal portions of the , and the occipito-mastoid suture is partly deficient in Skull II and replaced by a cleft in Skull III. The mandibular fossae are shallow in Skulls II and III. Sutherland12 suggests that the skull-base has not developed pari passu with the other parts, but examination of these skulls scarcely bears this out. Such deficiencies as the base shows seem to be quite in accordance with the deficiencies else- where. The defects throughout the skull seem coincident and proportionate; no area seems to present a primary disturbance. It is remarkable that in Skull I, a 16-year old skull, the basilar synchondrosis has already disappeared. Both externally and within this skull the sphenoid and occipital are united by osseous union though doubtless ossification has not extended through the entire depth of the cartilage. It is indeed a premature synostosis, yet no disturbance of the skull growth can be attributed to it. Certainly it cannot explain the brachycephaly, because brachycephaly is present in the other skulls in which the synchondrosis is still open. It would be more correct probably to say that synostosis is rather the result of the brachycephaly than the cause of it. In Skulls I and II the foramen magnum is slightly asymmetrical and in all it is of large size, 33x28 mm. in Skull I, 34x30 mm. in Skull II, and 31 X 26 mm. in Skull III. In Skull I the left occipital condyle is smaller than the right. The foramen ovale and the foramen spinosum are incompletely formed in Skulls II and III. and a foramen of Vesalius is present bilaterally in these but only on the left side in Skull I. In all, the anterior wall of the acoustic meatus is unossified over a limited area.

The thickness of the calvarium varies from 1-5 mm. to 334 Skull of the Mongolian Imbecile

3 mm., and though in Skull I the tables are relatively thick in proportion to the rather thin diploe, the component parts are less distinguishable in the other two skulls. The interior of the skulls is somewhat globular and the cerebral impressions are very slightly marked. The pituitary fossae are well formed, the dorsum sellae being particularly substantial. The measurements, in Skull I of 8x12x7 mm., in Skull II of 8 X 15 X 9 mm., and in Skull III of 10 X 13 X 5 mm. indicate a fossa of no small capacity. Of each of these skulls the atlas and epistropheus are preserved, and though in Skull I both are normal, in the other two skulls the development has been retarded and deficiencies indicate the foetal constituents of these vertebrae. Though in these skulls the orbital margins are certainly infantile there is no obliquity of the superciliary margins. Nearness of the eyes noted by Dr Thomson19 is difficult to measure, but my skulls do not show undue approximation of the orbits. In Mongolian peoples Keith32 states that the nasal region between the eyes is wide, flat and frequently sunken. The outward turning of the zygomatic arches, which considers a Shuttleworth7 characteristic, is not present in any of these skulls. " Brushfield35 writes : Various authors appear to agree that a certain arrest of development takes place at the base of the skull." My skulls do not warrant this supposition. What is lost in length of the skull-base is made up in breadth. The foramen magnum is large, the basilar process well-formed and there is no disturbing premature synostosis. Deficiency of the anterior wall of the acoustic meatus, imperfect closure of the foramen ovale and foramen spinosum, flatness of the occipital condyles, and in the youngest skull an indication of the component parts of the occipital bone are evidences of delayed development but are not features which have interfered with the growth or size of the skull-base. If any arrest of development has occurred it is in the brain not in the bones, and the skull-base is obviously capable of further growth and expansion had it been called upon for such provision. I cannot agree with Schuller20 that "there are frequently found defects in the line of the sutures" in the mongolian skull, but there is abundance of cartilage in the sutures of the chondrocranium as there is membrane in the membranous cranium. There is, however, a want of osteoblastic activity, and though bony growth is delayed the size of the skull is not interfered with 335 David M. Greig and accords with that of the brain. Before the age of 16 the growth of the mongol's brain has ceased. It is the nasal bones and the maxillae that are particularly affected, and this affection must begin early in intra-uterine life. According to Keibel and Mall21 the nasal bones, which are membrane bones, have a single centre which appears at the end of the second month. They describe the premaxillae and maxillae as being each developed from a single centre which appears in the sixth week of embryonic life and leads to union early in the third month. The ossification of the maxilla, Fawcett22 says, begins on the outer side of the nasal capsule and above the canine-tooth germ in the 18 mm.-stage embryo, i.e. between the sixth and seventh week. The nasal bones, maxillae and premaxillae, show restriction in development rather than interference with growth and contrast strongly with the mandible whose strength, size and shape are responsible, I think, for one of the characteristic features of the mongolian facies. That the disturbance of development is general seems to be attested by the coincident defects and deformities which are very commonly found in mongolian imbeciles. The short in comparison with the , the short broad and the tendency to ectropodactyly, and corresponding defects in the lower limbs are suggestive of achondroplasia and indeed there is a chondrodystrophy in mongolism in which the head and trunk, unlike achondroplasia, proportionately participate. It is probably some such consideration that has suggested a possible skull-base defect in mongolian imbeciles. Quite recently Jew-esbury24 and Myers26 have reported mongolism in one of twins and Reuben and Klein36 in both. Halbertsma27 has collected thirteen cases in which one of twins was a mongol, and in all the twins were of different sexes; he then refers to two cases in which the twins were of the same sex and in these both children were mongols. He does not produce evidence to support his supposition that these represent binovular and uniovular twins, and indeed his sug- is gestion untenable because Dr Coupland23 reports a female mongolian imbecile aged 11 years who was one of female twins, her sister being normal, and cites two similar occurrences recorded by Shuttleworth, one from Australia and the other from Scandinavia. What is at fault in these cases of maldevelopment ? Is it a gonadic defect able to initiate the foetus but failing to bring 336 Skull of the Mongolian Imbecile it to perfection, or does the weakness lie in the nourishing powers of the mother or in some ontogenic deficiency in the foetus? The osseous dysplasia is but an item in the general disturbance of growth. Observations of the placentae are not forthcoming. The other members of the family seldom show any abnormality. But mongolism is not a primary osseous dysplasia. The contrast between mongols and chondro- dystrophy (achondroplasia) emphasises that. One can conceive a local stimulus determining limited osseous peculiarities, overgrowths or deficiencies, but a general osseous disturbance can surely be best explained by failure of that supervising control which the nervous mechanism or the inherent correlated metabolism of the foetus itself exercises over all processes " involving general body growth. It is inconceivable," write Ormond and Williams,28 "that the derangement of an endocrine could be responsible not only for poor mental and physical development, but also for brachycephalic skulls, abnormally oblique epicanthic folds, congenital lesions, cleft palate, talipes, malformations of the , syndactyly, etc., all of which conditions are part of the clinical picture of mongolism." Even excluding cleft palate, talipes and syndac- tyly, which are by no means mongolian features, it may be difficult to conceive one endocrine being responsible for all this, but surely the failure in the supply of a combination of endocrines whose quantity, quality, and just proportion are necessary to normal growth is not an impossible conception. Indeed Englebach29 figures a typical mongolian imbecile as a case of thyreopituitarism. The condition is, he considers, a congenital hypothyreoidism to which is added later an anterior lobe pituitary deficiency. I doubt if we are justified in ascribing to either of these organs alone the definite role that author indi- 32 cates, though Keith considers the thyreoid as the centre of the growth-mechanism disturbance in the production of the Mongol. Even from the skull alone there seems evidence that development normally begun has mapped out all structures and features in the embryo but has failed to lead them to perfection during foetal growth, using the terms embryonic and foetal as understood by Ballantyne30 to indicate in the former a period of , in the latter a period of growth. The embryonic period lasts until the 40th day after impregnation, about the end of the 6th week of pregnancy. Strong31 quotes Mall that the first appearance of ossification in the skull appears in the maxillae on the 39th day. This is followed by VOL. XXXIV. NO. VI. 337 2 A David M. Greig the premaxilla three days later, while the centre for each does not appear until the 57th day. Obviously it is during this period that the departure from normal growth shows itself, and this failure in the bones is accompanied or followed by defective growth elsewhere, notably of the . Mongolism seems rather to be a defect in growth (foetal) than a defect in development (embryonic), and as regards the skull manifests itself in : 1. The readiness of the basilar synchondroses to become synostosed when the brain has early reached its maximum growth. 2. Brachycephaly with great relative interzygomatic breadth. 3. Poor development of diploe. 4. Various dental disturbances. 5. Defective alveolar growth without a sign of absorption. " " 6. A flat, broad, but infantile palate. 7. Limited growth of the maxillae and facial bones. 8. A broad and relatively well-developed mandible of modified shape. 9. Numerous anatomical peculiarities indicative of an infantile condition of the cranial and facial bones.

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