xxviii Journal of Comparative Neurology. 



Rkoions and Convolutions of the Prosencephalon. 



It may be remarked that the writer's suggestions respecting the dis- 

 tinctness of the basal part of the cerebrum, (that portion beneath the 

 rhinalis fissure) were quite independent of similar suggestions made by 

 Prof. W. Turneri and, being derived from studies in very different regions 

 serve to supplement the latter in various ways. According to Turner, in 

 all vertebrates it is possible to distinguish a basal region or rhinencephalon 

 and a dorsal or pallium which are separated by the rhinalis or ectorhinalis 

 fissure. The rhinencephalon consists of the bulbus and crus olfactorius 

 and the lobus hippocampi. The latter is always to be distinguished and 

 is bounded internally by the lissura hippocampi and cephalad i^y the 

 fossa Sylvii. The present writer has shown that the distinction between 

 that portion of the cerebrum ventrad of the rhinalis fissure and the mantle 

 portion is not only constant in lower vertebrates but that the infrarhinalis 

 region is different histologically. There is serious objection to the appli- 

 cation of the term rhinencephalon to this entire region, first, because it 

 has long been applied to the olfactory tuber; second, because there are 

 included cortical connective and peripheral structures under one head. 

 If, on the other hand, the writer's views as to the essential discreteness of 

 the pes and pero olfatorii are correct, the pero and the hippocampal lobe 

 are more intimately associated than the pes and pero and it remains to be 

 seen if the latter is not in reality i)ut a ganglion on the olfactory nerve 

 (radix lateralis). Much interesting matter on the convolutions is contain- 

 ed in the paper referred to. Ziegen who has also made a special study of 

 the convolutions- comes to quite different results, especially with reference 

 to the homologies of the convolutions in carnivora. 



The papers of Cunningham quoted in our literature give especially 

 interesting data respecting the transitory fissures which appear early 

 (only in the Primates) and persist until the fourth month when they 

 ■ either disappear or merge more or less completely into the definitive 

 fissures. On the lateral surface only the parieto-occipital and calcar are 

 permanent. These fissures are variable and asymmentrical. 



1. The fonvohitions of thclirain. .Iimnial of Anat. and Phys. Oct. 1890. 



2. Zur Vergloichendcn .\iiatoiiui' dei' lliriiwinduiigtii. Anal. Anxi'iger, V' 24, 

 1«'J(). 



