286 
ORIGINAL ARTICLES. 
A comparison of the casts (Figs. 1 and 2), and of the numbers 
given above as indicating the relative breadth of the cerebellum to 
the cerebrum, will probably strike the physiologist at first sight, as 
affording some corroboration of the usually received theory of the 
function of the cerebellum, viz. “ that of regulating and combining 
muscular movements.” The Gibbons, as is well known, are the most 
agile of the apes; the accounts we have received from good 
observers of the graceful ease and precision with which they take great 
leaps from bough to bough, sometimes catching with their hands such 
objects as a flying bird as they pass, are truly surprising; while, on 
the other hand, the heavy-bodied baboons generally confine their 
locomotive powers to walking upon the ground, or climbing among 
rocks. 
But physiological conclusions of any value, especially upon the 
most obscure and difficult of subjects—the functions of the different 
portions of the nervous centres, must be based upon much wider, as 
well as more rigidly exact observations. After comparing, as far as 
I have hitherto had an opportunity of doing, the relative size of the 
cerebellum with the motor powers of the various forms of quadru- 
mana, the conclusions arrived at are only negative. The active 
Gibbons have large cerebella, but the organ is equally well developed 
in the other anthropoid apes. The slower Baboons have a small 
cerebellum, but so also have the vivacious Cercopitheci and Maca¬ 
ques, zoologically allied to them. An individual of the species whose 
cerebellum is perhaps the most reduced of all, the Squirrel Monkey 
(Chrysothrix sciureus ), (Fig. 3) now living in the Gardens of the Zoo¬ 
logical Society, is, the keeper informs me, a lively little animal, 
capable of taking considerable leaps with great precision, and Hum¬ 
boldt’s testimony of its habits in its native state is to the same effect,* 
while the inert lemur-like Douroucouli ( JVyctipithecus ) has its cere¬ 
bellum tolerably well developed. In the greater number of the 
inferior Yertebrata, possessing more or less activity and power of 
combining and regulating their movements in running, leaping, flying 
or swimming, that portion of the cerebellum, the great development 
of which is characteristic of Man and the higher Quadrumana, viz. 
the body of the lateral lobes, is in a rudimentary condition, or en¬ 
tirely absent. When we consider the complex structure of this organ, 
and the extremely varying condition of its several component parts 
in the Mammalia alone, it is evident that it cannot be regarded as a 
whole in respect to its function, and further difficulties will remain 
behind, until physiologists have determined what kind of muscular 
actions in the living animal (whether, as Hr. Bolleston suggests,f 
* “ Ses mouvements sont pleins de graces. On le trouve occupe sans cesse a 
jouer, a santer et a prendre des insectes.”—Cours d’histoire naturelle des Mamrni- 
feres, par Geoff St. Hilaire, 1829, lOe Legon, p. 15. 
t Med. Times and Gazette, 1859, Vol. XL. p. 77; and 1860, Yol. I. p. 161. 
