Page 15. 
516 ON THE BRAIN 
upon the considerable development on the right side of bridging con- 
volutions, the great number of which in the brain of the Hippo- 
potamus is laid special strain on by Gratiolet,* who, whilst referring 
to the “‘ middle series” of convolutions, remarks :—‘‘Il acquiert une 
importance exceptionelle, et si son existence est au premier abord 
dissimulée, cela tient 4 la grande quantité de plis de passages verticaux 
qui lient cet étage supérieur a l’etage inférieur proprement dit.” On 
the left side these bridging convolutions do not exist, and as a result 
an extra longitudinal fissure is seen, which must be one of the typical 
sulci of the cerebral hemisphere, it being conspicuous in the brain of 
Hippopotamus liberiensis, according to Prof. Macalister’s outline sketch, 
though absent in the figures accompanying Gratiolet’s memoir on 
H. amphibius. 
The brain of the Hippopotamus is not richly convoluted. - It is 
about as much so as that of the genus Bos, decidedly less so than 
Camelopardalis girafia or the Camelide. The considerably smaller 
Rhinoceros, Ceratorhinus sumatrensis,t has more convolutions. 
Its weight immediately after removal from the skull was one pound 
and seven ounces. 
The most conspicuous fissure on the superior surface of the brain 
is one running from front to back, not far from the middle line, which 
it more nearly approaches anteriorly than posteriorly. This con- 
tinuous fissure must be compound, and made up of the coronal (co) 
in front, blended with the lateralis (1) behind, between which latter 
and the splenialis (sp) a secondary longitudinal fissure develops in the 
usual manner. Though, as far as I am aware, there is no other Ungu- 
late animal with the two above-named fissures actually joined, they 
are nearly so in the Camelidew, Camelopardalis, Dicotyles, and Bos. 
-Between the above-described fissure and the fissure of Sylvius 
there are, on the right side of my specimen, only transverse twisted 
conyolutions of considerable length, five or more in number, according 
to the way in which they are counted. On the left side an irregular 
longitudinal and fairly lengthy suprasylvian fissure exists, nearer the 
Sylvian than the lateral fissure, and therefore quite lateral in position, 
with several smaller sulci joining it. Having the typical Artiodacty- 
late brain before us, it is possible to recognize among these the descend- 
ing (ssd), posterior (ssp), anterior (ssa), and superior (sss) branches of 
the main fissure, the first-mentioned (if correctly identified) running 
in the direction so characteristic of the true Swine. 
The anterior branch of the suprasylvian fissure has no connexion 
* “ Anatomie de Hippopotame,” p. 325. 
+ “ Transactions of the Zoological Society,” vol. X. Pl. LXX. p. 411. (Supra, 
p. 143, pl. 4.) 
