When the gorilla is provoked, he displays both rows of teeth, and opens his mouth to utter sounds of fury, while making ready to fight. It is well known that anthropoids are able to pout and project their lips; and Darwin says that they do this, not only when they are slightly teased, and are sullen or disappointed, but also when anything occurs to make them uneasy. I have often observed in chimpanzees a slight wrinkling of the region of the nasal cartilage, and even a vibration in a lateral and upward direction. In any case, the muscles which we have described as acting on the nose and upper lip are exercised. The platysma myoides, which extends in man from the lower row of teeth to just below the clavicle, occupies about the same area in the gibbon and in other apes (Fig. 50). In the chimpanzee, however, this muscle extends as high as the zygomatic arch, or even higher. In the gorilla also I observed that this part extends comparatively high on the face. In chimpanzees, orangs, and gibbons the upper fibres of this muscle seem to form the risorius. In one case the platysma myoides sent forth a fasciculus, about 18 mm. in width, to the beginning of the lower temporal ridges. In the gorilla I saw that the uppermost fibres of the platysma myoides were partly covered by the risorius (Fig. 50, ~10~). From the corresponding muscle in the orang the lower fibres tend far backward, and are in connection with the deltoid muscle covering a segment of the capsular ligament. This muscle wrinkles the skin of the neck, and helps to draw down the lower jaw. In cases in which it extends far in an upward direction, as in those we have cited, it affects the lateral extension of the middle and lower skin on the faces of these animals, as well as the grinning contortion of the corner of the mouth. It may also have to do with the grumbling sound issuing from the throat-pouch, which is uttered by the animal when agitated, as he rapidly opens and closes his mouth. The strong sterno-cleido-mastoid muscle found in these animals, and especially in the orang and gibbon, can be divided without difficulty into a sternal and clavicular portion. The two portions diverge from each other in a downward direction. As Bischoff justly states, a muscle not hitherto observed in man may be traced in all four species of anthropoids, a muscle which extends from the external part of the clavicle to the transverse process of the first cervical vertebra. Bischoff has called it the musculus omocervicalis. It is found in other apes, although the site of its origin varies, sometimes occurring on the spine of the scapula. Our Munich anatomist differs from Huxley in regarding this muscle as “a brilliant proof of the relation of all apes with each other.” I give this assertion without further comment.