Cubical Anatomy of Several Ducts and Vessels by Injection Methods of Acrylic Resin V. Arterial distribution of the temporal muscle in some mammals By Tokuo Fujimoto Department of Anatomy, Osaka Dental College, Osaka (Director : Prof. Y. Tani g u c h i) (With 33 figures in 10 plates and one table.) Argument of this research was announced at 64th Annual Session of the Japanese Association of Anatomists, March, 1959, Tokyo. Preface On carotid arteries and their ramifications, anthropological and comparative anatomical or other works have been abundantly seen. But, those on the arterial supply for the muscle of the head and neck, from a different new point, are few. Especially no observation on the finer vascular distribution in the individual muscle has been made. The author has here undertaken cubical comparative anatomical study on blood supplying routes for temporal muscles of mammals easy to obtain and of human fetuses, by corrosion specimens of acrylic resin. Diverging features of all arteries from the external carotid or its branches taking part in this muscle, ramifications and anastomoses in the inner or outer part of the muscle, and distribut- ing territories of each branch in the muscle, are observed. The tem- poral muscle as well as the masseter, being rich in red muscle fibres, play a strong (dynamically) and important role in the mastication, and it is thought to be significant to throw light on the arterial distribution of them. Although, many comparative results of the carotid arterial system in mammals have been published, they can 389 390 Tokuo Fujimoto not be said to be faultless and perfect on the deeper part. And the human fetus was selected, because external carotid ramifications seemed to be fully studied in adults by many scholars, though not on each muscle. Encountering with unknown points on the compara- tive anatomy of the temporal muscle itself, the author felt many difficulties to perform this investigation, therefore, the muscle was dissected in advance. And especially on this point of rabbit and goat, the author will take it up in a separate paper to study on many more examples. The temporal muscle is most developed in carnivora, ruminant next, and rodentia poorest. On the human sub- ject, it developes rapidly in the first dentition stage of an infant, but in the fetal stage it should not yet grow enough, being poorer than that of rabbit, also in the function. Materials and Methods Following animals are used : 18 dogs, 12 cats, 12 rabbits, 10 goats and 11 human fetuses. The acrylic resin is injected into the common or external carotid artery (the vertebral artery ligated) of the body after depletion to death. The injection method published by T a n i g u c h i, O h t a and T a j i r i ('52) and its supplement ('55), are adopted. Tissues of the injected head are digested with thick NaOH solution after curing the resin to make corrosion specimens. While, for the dissection, a few of injected heads in each species are preserved in formalin solution without digesting tissues. Since the cured resin injected into finer parts is somewhat fragile for the dissection, aceton solution (14%) of the polymer is employed in order to prevent breaking. This material is better, being more elastic and tolerable to the movement of surrounding tissues resulting from the dissection. Through the dissection of the muscle, relations between supply- ing arteries and other organs or tissues are observed. Corrosion specimens are used comparing them with dissecting specimens at every step. Distributions of these arteries in layers of the muscle are observed at each different digesting stage of tissues. For the observation and micrometry of finer portions, the microscope and binocular magnifier are employed. Arterial Distribution of Temporal Muscle 391 Observations On each species of the animals, branching features of all arteries supplying the temporal muscle, relations to their sources and adja- cent branches, distributing appearances within the muscle, anasto- moses (mainly above 50 au.in thickness) with others and the distri- buting region of each branch, are described here. Anatomical views, which are not enough to know from references concerning with the temporal muscle, will be respectively supplemented briefly at first. Dog : Among the animals observed, the temporal muscle of dog as well as of cat is the strongest, composed of the superficial and deep layers, though both can not clearly be classified. Arteries supplying this muscle are four, the posterior auricular, the superficial temporal, the posterior deep temporal and the anterior deep temporal. 1. Posterior Auricular Artery (Figs. 1, 2, 3 and 4) Thicknesses at the root are 1.5-2.4, M. 1.8 mm.. This artery ori- ginates from the supraposterior convex wall of the external carotid (2.8-4.0, M. 3.0 mm.), which goes around a sharp curve anteromedially between Bulla ossea (E 11 e n b e r g e r, 1891) and Proc. postglenoideus of the temporal bone. It takes course at first backwards 8-12 mm. along the outside of the bulla, gets to between the base of the jugular process (occipital) and the lateral end of the superior nuchal line, bending upwards (the first curvature, its convex faces infra- posteriorly), and turns to the posterior (the second curvature, its convex faces to the supranterior) (Figs. 1, 2 and 3). R. mastoideus and R. auricularis posterior at the first curvature next to A. stylomastoidea, and R. auricularis anterior just before the second curvature, originate respectively. In literature, branches distributed to the temporal are reported only on R. temporalis post. s. occipitalis (E 11 e n b e r g e r), but the author observes four branches and calls them as follows in their diverging order : Rr. musculares temporales primus, secundus , posterior et anterior (Figs. 1, 2, 3 and 4). 1) R. m. temp. primus (0.69-1.05, M. 0.87 mm.) branches at the first curvature of the posterior auricular artery, having a relation- ship with the mastoid ramus and the posterior auricular ramus as 392 Tokuo Fujimoto follows : They diverge at the same point, on 14 examples in 24 ; the posterior auricular ramus diverges from this muscular branch, on 8 exs. ; the mastoid ramus diverges from this muscular, on one ; or all diverge with one common stem, on one (Fig. 1). Under the above- mentioned relations, this branch, originated from the lateral wall of the mother artery, meanders along the posterior margin of the muscle drawing an arch. After reaching the supraposterior corner of the muscle, it runs forwards along the sagittal margin (crest) (Figs. 1 and 4) and gets to the supra-orbital margin. Supplies en route are to the fascia and the superficial muscle part of the supra- posterior and nearby the superior margin, while, one or two branches are given to the superior nuchal muscles and subcutis, and one small branch to auricular muscles. 2) R. m. temp. secundus (0.37-0.74, M. 0.51 mm.) is the smallest. Branching from the lateral wall at the second curvature of the pos- terior auricular artery, it proceeds right upwards. Between the auricle and temporal muscle, its main current is distributed to auri- cular muscles and subcutis. One weak branch, drawing a small semi- circle before R. m. temp. primus, is distributed just before the area of the primus (Figs. 1, 2 and 4). 3, 4) Rr. mm. temp. posterior (0.68-1.24, M. 0.91 mm.) et anterior (0.5-1.11, M. 0.74 mm.) are branched via a very short (7-9, M. 8.2 mm.) and S-shaped common stem medialwards from 2-4 millimetres posterior to the second curvature of the posterior auricular artery. Then, penetrating the fascia at the infraposterior corner to get to the bony surface, the stem divides into two. The posterior takes its course to the supraposterior in the muscle and goes up along the posterior margin of it. The anterior proceeds antero-inferiorly or anterosuperiorly (Figs. 1, 2, 3 and 4). Both are main streams dis- tributed to the posterior 1/3 of the muscle. The posterior sends out at first a branch in all cases from the lateral wall at the infra- posterior corner, which again penetrates out the muscle onto its surface and runs to the supranterior beneath the fascia (Fig. 4). It supplies the lower superficial layer of the posterior 1/3 of the muscle. Next to this, en route the posterior reaches the supraposterior corner of the muscle, 2-3 parallel branches rise regularly to the anterior or supranterior, and serve the posterior 1/3 of the muscle (Figs. 1 and 2). At the supraposterior region, they anastomose (c. 124 it) with branches split supraposteriorly from the superficial temporal artery. The anterior takes a stand with the posterior anteroposteriorly, direct- Arterial Distribution of Temporal Muscle 393 ing to the antero-inferior or anterosuperior (Figs. 1, 2, 3 and 4). Branches of it are shown, at first, emerging along the ventral mar- gin of the muscle, and then, 2-4 rungs directing to the anterior and posterior regularly with almost the same intervals (Figs. 1 and 2). They anastomose (c. 155 /1) with the supraposterior branch of the pos- terior deep temporal artery in the deep superior portion of the muscle centre, and near the ventral margin of the muscle, several upper and lower parallel branches (120-150 A) anastomose rung-shap- edly with the periphery of the posterior branch of the posterior deep temporal artery (Figs. 1 and 2). 2. Superficial Temporal Artery (Figs. 1, 2 and 3) Thicknesses are 1.4-2.0, M.