144 SANGUIFICATION. LECT. VII. 



Boussingault has proved by experiment that, in the urine 

 of the horse, is found all the azote which formed part of its 

 food; and he has thereby demonstrated, that the excess of 

 azote expired equally proceeds from Jhe aliments. 



It is impossible, in the present state of science, to say 

 precisely through what series of modifications and inter- 

 mediate products, the muscles, cartilages, &c., pass, in 

 order to be converted into urea under the action of the 

 oxygen of the blood globules. By adding to the formula 

 of proteine, which at the same time is also the formula of 

 albumen, caseine and fibrine, as much oxygen as is neces- 

 sary to convert it into urea, and to convert the excess of 

 hydrogen and carbon into water and carbonic acid, we 

 obtain quantities of carbonic acid and water which are 

 much smaller than those produced by respiration. Here 

 is a numerical example deduced from the experiments of 

 Boussingault, which I give you the better to establish 

 the fact, that the carbon of azotised foods converted 

 into urea, is much less than that which animals produce 

 in the form of carbonic acid. The following are the 

 numbers: a horse was kept in a perfect state of health, by 

 eating daily 1\ kilogrammes of hay and 2 kilogrammes of 

 oats. Analytical researches show that the azote of the hay 

 is 1*5, and that of the oats 2*2 per cent. If we assume 

 that all the azote of the aliments is reduced in the blood to 

 the condition of fibrine and albumen, there would then be 

 140 grammes of azote introduced into the blood, and 

 destined to replace the azote which goes out in the pro- 

 ducts of the transformed tissues. The quantity of carbon 

 taken simultaneously with the azote [in the fibrine and albu- 

 men] amounts to 480 grammes ; and of those only a portion 

 can be converted into carbonic acid during respiration, 

 since the horse converts part of the carbon into urea, and 

 a portion into hippuric acid. But a horse, according to 

 the experiments of this chemist, evolves by respiration in 



