86 Journal of Comparative Neurology. 



The dorso-lateral aspect (Fig. 33) shows the preinsula to con- 

 sist of three gyres while the postinsula has but one. The gyres 

 of the insula are in general simple. One specimen, however, 

 showed the caudal gyre (postinsula) subdivided into three parts. 

 The fissures grow deeper as they approach the meson except 

 the transinsular but it is not known that any are constant. The 

 sheep brain exhibits two unusual conditions shown in the tran- 

 section of this brain (Fig. 34) : first, that a bundle of myelinic 

 fibers enters the insula from which it might be inferred that this 

 area is functional, or at least assists in the performance of a 

 function. These fibers seem to pass principally to the dorso- 

 lateral part of this area, although it is evident that many are 

 given off along its course to other parts of the area mostly 

 dorsad. Secondly, there is no indication of a claustrum. It 

 is not believed that any great significance can be attached 

 to the apparent absence of this part in the sheep other than 

 that the insula in this animal is relatively farther laterad than 

 in those where the claustrum becomes so demarcated and hence 

 the fibers from surrounding areas which in some other animals 

 pass through the cortex here pass wholly mesad. The blood 

 supply is derived wholly from branches of the medicerebral 

 artery which extend over the surface. The position of the 

 rhinal fissure and the relations of the insula to the olfactory 

 tract are clearly shown. The myelinic fibers of the latter ex- 

 tend only to the bottom of the rhinal and in no case have fibers 

 been found extending upon the insular area. This fiber area of 

 the olfactory tract extends considerably farther ventrad than 

 shown (Fig. 34) and at the ventral end the fibers are most 

 numerous and collected into a bundle of considerable size. 



The insula of the cow (Figs. 26-29) is well developed, ex- 

 posed on the lateral aspect and lies almost wholly within the 

 Sylvian fossa. It presents in this animal peculiarities not pre- 

 viously met with. The area in but one of five specimens was 

 completely divided into a preinsula and a postinsula. In this 

 one (3362) the transinsular fissure was well marked, was deepest 

 at the latero-ventral end, and was continuous mesad with the 

 circuminsular. The fissure cephalad of the transinsular also 



