48 ZOOLOGY. 



but neither a central nucleus nor external envelope is to 

 be seen. 



83. Composition of the Blood. The composition of the 

 blood is very complex. In the higher animals we find water, 

 albumen, fibrin, a colouring matter containing iron, a yellow 

 colouring matter, several fatty substances, as cholesterine, 

 cerebrine (a substance containing phosphorus) ; many salts, 

 as chloride of sodium or sea salt, sulphate of potass, 

 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 acids; 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 arc 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 



