- 
1819:] and on the Blood in genertl. 978 
satisfactorily ascertain ; butit has usually been considered as analo- 
gous to the saliva; andif this opinion be correct, it may be safely 
considered as containing noalbumen. The changes produced in 
the digested alimentary matters by these fluids are evidently of 4 
chemical nature. A gaseous product is usually evolved; a distinct 
precipitation of the biliary principle in apparent union with some 
others, chiefly of an excrementitious nature, takes place ; the 
mixture becomes neutral; and an albuminous principle ts formed, 
at least, traces of this principle appear, which, however, become 
much more distinctly visible at some distance from the pylorus.* I 
tried to produce these changes out of the body, and with this 
view mixed a portion of the fluid obtained from the contents of 
the stomach of the rabbit, formerly described, with a portion of 
the bile of the same animal. A distinct precipitation took 
place, and the mixture became neutral ; but although I thought 
that the resultme fluid was more of an albumimous nature, yet 
the formation of a perfect albuminous principle was doubtful ; 
probably the presence of the pancreatic juice was necessary to 
complete the formation of this principle.+ The proportion of 
this albuminous principle, after a certain distance from the 
pylorus, decreases rapidly as we descend the alimentary canal, 
and at length nothing is left but excrementitious matters, con- 
sisting chief, of the undissolved parts of the food, combined 
with the mucus of the intestines, and the biliary principle some- 
what altered in its nature. Further changes, the nature of 
which is not very well understood, take place in these matters, 
more especially in the cceca and large intestines of those animals 
which feed on vegetable substances. Here it is they assume the 
usual excrementitious appearance. Some think that various 
matters, noxious to the economy, are excreted here ; while others 
consider this part of the alimentary canal to be a sort of second- 
ary stomach, intended to digest those substances which escape 
the solvent power of the first. Both these opinions may be in 
part correct. 
The phenomena of chylification have been still less satis- 
factorily observed than those of chymification. It seems, 
* Itis true that in two of the specimens of chyme, that, namely, of the dog fed 
on vegetable food, and that of the ox, described in a former part of this paper, no 
traces of albumen were obtained. From my not haying collected either of these 
specimens myself, I cannot be supposed tu be able to account satisfactorily for this 
‘circumstance. In the first instance, the dog had been fed on a species of food 
which was uunatural to him, and the quantity of albumen was small, even in the 
chyle of the same animal; probably, therefore, the whole had been taken up from 
the intestines. In the other instance, the ciyme had been kept for some time before 
Texamined it, and, besides, seemed to contain an unnaturally large proportion of , 
bile.~ My not finding albumen in these substances occasioned me to consider its 
presence to be much tess general than I have since found it, and to be probably 
confined to the carnivorous animals, : 
_ + I by no means wish to be understood to assert, that the bile and pancreatic 
juice are the sole agents operating to produce this change; the vital action of the 
duodenum itself must be probably taken intg account, 
Vou. XIII. W° iV. 8 
