THE RELATION OF DIET TO DISEASE 449 
metabolism to its nitrogen supply; the adjustment 
requires an appreciable amount of time. A diet changed 
to a lower nitrogen level results in a continued loss of 
nitrogen, increased combustion of fats and carbohydrates. 
The animal makes no apparent effort to reestablish 
equilibrium, and sooner or later digestive disturbances 
and loss of strength occur. 
If, on the contrary, the protein is steadily increased 
after an animal has established equilibrium, the nitrogen 
metabolism increases and the level of nitrogen equilibrium 
risestohigherandhigher levels. There is, at the same time, 
a lowering of the fat combustion, an increase in the respir- 
atory quotient and in the heat production. The excess 
protein must be split, deaminated, burned and eliminated. 
Fifty-five per cent, of the intake is converted into glucose 
which is burned and the excess stored as glycogen. The 
sulphuric acid formed during the protein cleavage is 
neutralized by the body alkalies. In these cases the liver 
is often congested and enlarged. The urine shows excess 
of urea and ammonia. At times the excess, being so great 
that it cannot be absorbed, undergoes chemical and bac- 
terial decomposition which causes digestive disturbances, 
torpor and constipation. 
The organisms associated with protein food are 
usually the putrefactive types which break the protein 
molecule into the aromatic bodies, phenols, indolacetic 
acid, indolpropionic acid, skatol, etc. These bodies on 
absorption are believed to give rise to hypertrophy of the 
adrenal, interstitial changes in the kidney, and arterio- 
sclerosis. Another group of substances, pressor bases 
and amines, are manufactured by certain anaerobes 
acting on proteins. These, when fed by mouth, are detoxi- 
cated by the liver cells, but when formed below the portal 
circulation, give rise to anaphylactic phenomena — 
urticaria, etc. Certain other organisms give rise to 
soluble toxins as in botulism and thyrotoxicon poisoning. 
