
1890.] Remarks on the Brain of the Seals. 121 
are more numerous, constant, and of classifying value in a com- 
plex organ such as the brain than in the spinal cord. Yet even 
in this comparatively simple organ specific differences of struct- 
ure are found, and accordingly the most atypical form is repre- 
sented in the Cetacea. The ventral horn of gray matter is im- 
mensely overgrown, and the dorsal correspondingly atrophic ; 
there is an enormous lateral horn present. On first sight this 
would appear to be an entirely novel structure, peculiar to the 
Cetacea; further examination shows that it is homologous with, 
though an overgrown representative of, a cell-group present in 
other mammals, which owes its prominence and peculiar position 
to the following factors: (1) The shrinkage of the neck of the 
dorsal cornu acts on the extreme ventral and lateral parts of the 
ventral horn as would the passing of an elastic band around a 
group of matches, spreading their ends apart; (2) the absence 
of the pyramid tract in the dorsal part of the lateral column 
causes an encroachment of the ventral part of the lateral column ; 
(3) the dorsal (posterior) white columns are relatively reduced. 
To convert a human cord into a porpoise’s there must be imag- ' 
ined a shrinkage of the posterior or dorsal white and gray 
matter, as well as the posterior or dorsal part of the lateral 
column, in other words, of the entire part of the cord which 
would lie behind a transverse line which in man leaves nearly as 
much in front (ventrad of) the central canal as behind (dorsad of ) it. 
This line in the Cetacea would be a curve, and in accordance 
therewith the outline of the cord in the latter is not nearly cir- 
cular or a rounded quadrangle as in man, but heart-shaped, the apex 
being represented by the shrunken posterior or dorsal segment, 
the bifurcate base by the overgrown halves of the ventral or 
anterior segment.” Although this remarkable deviation is in 
compact, massive kind, in distinction to the slender lamina type characteristic of 

in bulk without crenulation; yet the latter presents true Ungulate features. 
16 The spinal cord of the gorilla in the dorsal region (Waldeyer) shows characters not 
found in the human cord, a fact long known to me, though not published, from the case 
of the chimpanzee. 
17 Guldberg has partly observed this, but many years subsequently to my published 
observations, with which h to have been unacquainted. 

