ANATOMICAL STRUCTURE OF ANTHROPOID APES. 159 



in Fig. 3, also drew down the corner of his mouth 

 when he was pleased, by means of the muscular 

 system which we have just described. 



When the gorilla is provoked, he displays both 

 rows of teeth, and o})ens his mouth to utter sounds 

 of fury, while making ready to fight. It is well 

 known that anthropoids are able to pout and jiroject 

 their lips ; and Darwin says that thny 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 begin- 

 ning 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 



