518 MR. youatt’s veterinary lectures. 
the healthy or diseased state of the frame. The accumulation or 
«/ 
absorption of the adeps is a matter of little consequence else¬ 
where ; but in sickness and in health the bulk of the brain must 
remain unchanged : there must be no in-crease of substance to 
press upon the origins of the nerves—there must be no loss of 
it to create a vacuum, or to produce engorgement, or, perhaps, 
rupture of the vessels. 
The Chemical Composition of the Brain. —I find an appa¬ 
rently pulpy mass which has little interposed cellular or adipose 
matter. When I triturate this pulpy matter, I can form a per¬ 
fect emulsion that will pass through the finest sieve. I coagu¬ 
late it by heat or by acids, and I find that the coagulum is dif¬ 
ferent from that which can be produced from any other similar 
substance ; it consists of mingled albumen and oil, and with none 
of that which we almost regard as the principle of animal mat¬ 
ter—nitrogen. In place of this, I discover something which no 
other partof the frame will yield—uncombined phosphorus; and 
this albumen and oil, with one-twentieth part of the various salts 
of potassa, sodium, lime, and magnesia, and one-sixtieth part of 
osmazome, make up the solid part of the brain. The cerebral 
mass is composed of one part of all these solids combined, and 
four parts of water. While, therefore, I trace to the brain a 
peculiar function, I find a peculiar composition. There seems 
to be little or no difference in the chemical composition of the 
cortical and the medullary parts. I have ventured to assign to 
them a difference in function ; this theory, however plausible 
and interesting it may appear at present, and firmly as I may 
now be disposed to believe in it, may hereafter be discovered to 
be as untenable as that which assumed that the cortical portion 
consisted of a congeries of bloodvessels for the production and 
nourishment of the medullary part, W'hereas the latter had al¬ 
most attained its full development before a trace of the former 
could be discovered. The microscope has also ascertained, that 
instead of the larger arterial branches being found in the cineri- 
tious, and their minute ramifications dipping into the medullary, 
the vessels of the medullary portion are considerably larger than 
those of the cortical. But I must proceed to the enumeration 
(it will be little more) of the tubercles, and cavities, and irregu¬ 
larities of the brain. 
The Corpus Callosum. —Having stripped off the dura mater, 
and holding the hemispheres a little apart, I observe a white 
convex body occupying the bottom of the sulcus. It has the ap¬ 
pearance of the crown of a compressed arch, and so it is : it is 
the central portion of the roof of two cavities, which I shall have 
presently to describe—the lateral ventricles*. This is the corpus 
