= —_—————_—_ 
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THE PRINCIPLE OF VITAL AFFINITY. oo 
excretions, although it can only be through the excretions that they disappear 
from the body, and although the earthy or saline matters absorbed from the tex- 
tures are there found. The animal compounds existing in the textures must 
therefore have undergone a great chemical change, in the process by which they 
are removed from their place in the living body, and finally expelled from it; and 
this notwithstanding that they are placed in circumstances exactly similar to 
those, in which their previous original separation and deposition from the blood 
in the minute capillaries took place. 
2. The substances into which these animal compounds (with or without ad- 
ditions derived directly from the prime viz) have resolved themselves almost en- 
tirely before they are thrown off in the excretions, must be, the water which is the 
basis of all, the carbonic acid thrown off by the lungs and skin, the choleic acid 
thrown off by the liver, and the urea and uric acid thrown off by the kidneys. 
All these last we know to be formed in the course of the circulation, not in the or- 
gans by which they are separated from the blood ; and all possess these essential 
peculiarities, distinguishing them from the compounds forming the textures ; 
Jirst, that they are crystallizable, z.¢., the elements composing them are so ar- 
ranged as to be capable of assuming the definite forms peculiar to inorganic 
matter; and secondly, that they are poisonous to the living body when they are 
allowed to accumulate in the blood, and, therefore, that their continual expulsion 
is essential to life. 
3. When we farther examine these compounds, into which the animal tex- 
tures have resolved themselves before they are expelled from the body, we 
find that they are substantially the same as those, into which these textures are 
ultimately converted after death, by help of union with oxygen, when in contact 
with air and water, and at a certain temperature,—viz., water, carbonic acid, and 
ammonia, the small quantities of sulphur and phosphorus contained in the ani- 
mal textures, combining likewise with oxygen so as to form sulphuric and phos- 
phoric acids before they are expelled. 
C N H O 
Thus Urea consists of 100 100 200 100 
Add water, bets see 100 100 
100 100 300 200 =Carbonic acid and ammonia. 
Again, choleic acid consists of 76 2 60 2 
Subtract urea 2 2 4 2 
74 ae 56 20 Adding oxygen freely, 
184 
We have, 74 Abed 56 204 =74 CO, + 56 HO carbonic 
acid and water. 
VOL. XVI. PART III. 4p 
