8 Journal of Comparative Neurology. 



ever, in fig. 2, it will be noted that the lateral surface of the 

 insula is exposed in two areas which although connected are 

 quite distinct. The intervening space in which the insula is 

 exposed can be no less than the Sylvian fossa. In brains hav- 

 ing more highly developed frontal lobes, this fossa is limited, in 

 the adult, by the development of the pre-and sub-operculums, 

 to a small portion cephalad of the temporal lobe. The width 

 of the fissure which Turner calls rhinal, cephalad of its junction 

 with the Sylvian fissure, is always greater than its width caudad 

 of the Sylvian or cephalad of the fissure P. (fig. 2) where it is 

 the true rhinal fissure. This increase in width is probably due 

 in most cases to the entering of numerous blood-vessels which 

 transverse the insular area and these go mainly to its dorsal sur- 

 face. I think therefore that Professor Turner erred in naming 

 this the rhinal fissure instead of Sylvian fossa, as the rhinal fis- 

 sure extends ventrad of the insula and the crus is not connected 

 with the insula at its lateral surface. 



Huxley (Anatomy of the Vertebrated Animals, p. 61, 

 Fig. 21) figures (see Fig. 3) the left half-brain of a pig and rep- 

 resents the insula as normally exposed in the Sylvian fossa. 

 Krueg^ says ' ' the so-called insula, as in the carnivora as well as 

 in the pig (presumably all Suillidae), lies concealed in the depth 

 of a fissure, while in the remaining ungulates it is exposed." 



In sixteen brains of pigs ranging one year and under, 

 nearly three-fifths of the insulas were entirely concealed, while 

 in the remaining two-fifths the areas of exposure differed greatly, 

 the extreme being shown in Fig. 2. In five brains of pigs be- 

 tween one and two and a half years, all insulas were entirely 

 concealed and the conclusion reached was that the insula is not 

 normally exposed in the pig. There is considerable variation 

 in the insulas of the same brain. 



In No. 9, Left exposed. Right concealed. 



In No. 13, Left scarcely exposed (?) Right exposed in two 

 places, Fig. 2. 



In No. 17, Left exposed. Right concealed. 



I. Ueber die Furchung der Grosshirnrinde der Ungulaten, in Zeitschrift 

 ftir Wissenchaftliche Zoologie, Vol. 31, p. 313. 



