Clark, Comparative Anatomy of the Insula. 89 



over the dorsal surface and almost completely divides the pre- 

 insula upon the lateral surface. 



The insulas of the "Sage horse" (Fig. 25) consist of 

 five gyres each, of which three belong to the preinsula and two 

 to the postinsula. Before dissection the left insula showed four 

 gyres exposed while the right showed three. One of the main 

 branches of the medicerebral artery lies in what I have called 

 the transinsular fissure (Fig. 25). This fissure is well marked 

 on both sides. In the left insula the two most cephalic gyres 

 are nearly perpendicular, while the other three are at an angle 

 of about 60° to the lateral surface. On the right all the gyres 

 are in about the same plane which lies nearly perpendicular to 

 the lateral aspect. Those of the postinsular seem better devel- 

 oped and the first gyre of the postinsula is the one most ele- 

 vated. There seems to be an approximation to a pole in this 

 specimen not found in any other animals than the primates. 

 The second gyre is also the smallest as in man. 



The insular region of the tapir {Tapirus malayamis, Fig. 

 31) presents a very peculiar appearance, from the fact that be- 

 tween the area which I have called the insula and the rhinal fis- 

 sure there seems to have arisen a corrugated area which is not 

 believed to belong to the insula at all. This area extends from 

 the frontal to the extreme end of the occipital lobe and through- 

 out its course lies just dorsad of the rhinal fissure which is in- 

 terrupted at several points on the left side but is continuous on 

 the right. The fissure dorsad of this area is nearly parallel to 

 the rhinal except near the caudal end. The area included be- 

 tween these two fissures is fissured, but only slightly elevated 

 above the olfactory tract, and is continuous with the insular area. 

 The insula in this specimen is only slightly elevated and con- 

 tains but two gyres of which the more cephalic is the larger. 

 The fissures are simple and very shallow ex«ept the circuminsu- 

 lar at the cephalic end. The transinsular is not well marked 

 near the mesal margin. The insula is entirely concealed. 



In 1878 Krueg (30, 325) said the insula was present in the 

 Hippopotamidae. Chapman in 1881 (y, 144) said: "The 



