Edinburgh Medical Journal June 1927 THE SKULL 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 skulls 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 Cephalic index 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 face 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 bones 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 craniometry 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.