44 ZOOLOGY. 



carbonate of soda, hydrochlorate of potass, hydrochlorate of 

 ammonia, the carbonates of lime and magnesia, with phos- 

 phates of soda, lime, and magnesia : the lactates of soda, the 

 alkaline salts formed by the fatty adds : finally, free carbonic 

 acid, nitrogen, and oxygen. But this complexity, great though 

 it be, is yet below the reality, for there certainly exist other 

 substances in the blood which chemistry cannot demonstrate, 

 by reason, probably, of our imperfect means of analysis. By 

 arresting, for example, the secretion of the urine from the 

 blood, various matters will then be found mixed with the 

 blood which could not be previously detected, but which are 

 presumed to have been present under the same or other un- 

 known forms. 



The substances enumerated as entering into the compo- 

 sition of the blood, compose nearly all the parts of the animal 

 economy : the albumen forms the basis of many tissues, the 

 fibrin is the constituent part of the muscles, and the salts 

 enter into the composition of the bones and of many hu- 

 mours ; and from the whole of the facts known, it may be 

 safely concluded, that the materials destined to become flesh, 

 bile, urine, &c., already exist in the blood, the organs which 

 are to appropriate them merely drawing them from the blood, 

 but not forming them : and thus there exists some reason 

 for calling the blood, liquid flesh. 



84. The proportions in which these constituent parts of 

 the blood exist, vary much in different animals ; and as 

 regards the solid and liquid elements, they may differ in the 

 same individual at different times. In man the globules are 

 more numerous, and the watery part less than in woman ; 

 temperament also exercises some influence in this respect. 

 In 100 parts of the blood in man, we find 79 parts of water, 

 19 of albumen, 1 part of salts, with some traces only of fibrin 

 and colouring matter. In birds, the proportion of water in 

 the blood is less; but in the batrachia and in fishes the 

 amount is greater In the frog, for example, there are 88 

 parts of water in 100 of the blood. 



Analogous differences are observed in comparing the relative 

 qualities of the serum and globules of the blood in different 

 animals; while as we shall subsequently see there exists a 

 remarkable relation between the amount of the globules and 

 the animal heat. Birds, of all animals, have the blood richest 

 in red globules, and in them the animal heat is greatest. 

 Mammals, less warm than birds, have from 7 to 12 per cent., 



