94 APPLIED PHYSIOLOGY 



animal food are phosphates; those of vegetable foods, 

 carbonates. The blood of herbivorous animals is there- 

 fore rich in the latter, that of carnivora in the former, 

 and the acids formed in the tissues will form bicarbonates 

 in the blood of the herbivora, and acid phosphates in 

 that of carnivora. Now, acid phosphates hold earthy 

 phosphates in solution, and bicarbonates dissolve earthy 

 carbonates. Hence the urine of carnivorous animals is 

 rich in phosphates of lime and magnesia, that of the 

 herbivora in calcium and magnesium carbonate. 



The molecular concentration of the blood is isotonic 

 with a 0*9 per cent, solution of common salt, and it 

 tends to maintain this degree of concentration with great 

 constancy. It takes a very large loss of fluid from the 

 body to render the blood appreciably more viscid, but 

 this does sometimes occur, as, for instance, in the case 

 of choleraic diarrhoea. 



In addition to its saline ingredients, the plasma also 

 contains, as one would expect, traces of various soluble 

 substances on their way to and from the cells. Chief 

 amongst these are urea, sugar, and fat, but many other 

 substances are represented in traces. The exact amount 

 of these ingredients must naturally vary greatly from 

 time to time. Sugar, for instance, normally amounts to 

 about 1 part per 1,000, but may rise above this after an 

 excessive consumption of carbohydrates. Fat is usually 

 present to the extent of 0'75 per cent., but after a meal 

 rich in fat this amount may be greatly exceeded. Where 

 the body fat is being utilized as food also, the amount in 

 the blood on its way to be consumed may rise consider- 

 ably. Thus, it may be very high in cases of cesophageal 



