524 MR. youatt's veterinary lectures. 
interpositum. Placed over this foramen,and between the thalami 
and behind the quadrigemina, is the pineal gland. It is a small 
pear-shaped reddish-grey body, enveloped in folds of the pia 
mater ; and, not only by means of the pia mater, but distinct 
pedunculi proceeding from itself, connected with almost every 
neighbouring part, and also with some distant tracts of the brain. 
Its little peduncles are traced without much difficulty ; they look 
like nerves proceeding from it. Observe them running over the 
thalami, and penetrating even to the crura of the fornix, and 
then consider with how many and how important parts of the 
brain these are connected. We term it a gland, for it is sur¬ 
rounded by a plexus of vessels, with which it is intimately asso¬ 
ciated, and which may be traced into and from it. Galen thought 
that it was the very seat of the soul; others have assigned an 
inferior office to it, namely, that of a manufactory or reservoir 
of serous fluid separated from the blood. I must honestly con¬ 
fess that I know nothing about it; but when I see it so con¬ 
nected, so curiously organized, and so securely defended, I am 
persuaded that it does discharge some important function, which 
a more fortunate inquirer may probably be hereafter enabled to 
develop. In the hare and rabbit it seems to be more decidedly 
vascular than in any other domesticated animal; and although I 
have not been able to find in the horse the gritty, sandy matter 
of which human physiologists speak, this is abundant enough in 
some of the rurainantia, and particularly of the’deer kind. 
The Corpora Quadrigemina. —Behind the pineal gland, the 
fornix, and the corpus callosum, are four eminences, the corpora 
quadrigemina. We know not their function, but it must be an 
important one, for they are the first portions of the medullary 
matter that appear. They are earliest seen in the form of two 
little tubercles, distinct from each other; by degrees a well-de¬ 
fined channel appears between them, and, at a still more advanced 
period of utero-gestation, a transverse line is discovered dividing 
each of them into two, and completing the corpora quadrigemina. 
They are important, however, in comparative anatomy, as unerr- 
ingly pointing out the class to which the animal belongs. 
2'he Nates and Testesy considered with reference to Compara¬ 
tive Anatomy. —The tubercles are divided into the nates and 
tedesy of which you may perhaps form some idea from a reference 
to the following singular fancy of anatomists. They supposed 
this portion of the human brain to bear some resemblance to the 
posteriors of an hermaphrodite,—the vulva is the foramen com¬ 
mune anterius, the anus is the foramen between the soft and the 
superior commissures, and then the division of the tubercles will 
answer to the relative situation of the nates and testes; the 
