THE ESSENTIAL PHENOMENA OF CIRCULATION. 



19 



FIG. 6. 



and called haemoglobin. The quantity of iron exist- 

 ing in the blood of an adult man does not exceed a 

 drachm. 



The plasma contains, for every eight hundred and 

 seventy-five parts, seven hundred and ninety parts of 

 water and sixty of albumen, the remainder being made 

 up of small quantities of more than fifty different sub- 

 stances, each of which either is 

 required to repair the waste of 

 certain organs, or is the waste 

 product eliminated from some 

 organ. 



The blood has not the same 

 appearance and the same compo- 

 sition in all animals. It has a 

 red color only in the vertebrates 

 and in certain annulates belong- 

 ing to the group of worms. In 

 all other cases it is whitish, 

 bluish, yellow, green, or violet. 



The corpuscles of different ani- 

 mals differ also in shape, size, 

 and relative number. Only mam- 

 mals have round corpuscles ; in 

 other animals the corpuscles are 

 elliptical, and possess a nucleus 

 which very rarely exists in the 

 red corpuscles of mammals. Their 

 size has no relation to that of the individuals : thus, 

 in the horse they are -g-jVo" ^ an mcn ^ n diameter, in 

 the snail 25 1 00 inch, and in man -%$-$ inch. The long 

 diameter of the elliptical corpuscles of the frog is T yVrr 

 of an inch. Lastly, if we study the proportion of these 



RED BLOOD-CORPUSCLES, 

 highly magnified. 1, cor- 

 puscles seen on their broad 

 surface ; 2, seen on their 

 edge; 3, rolls of corpuscles, 

 indicating the manner in 

 which they are frequently 

 observed to arrange them- 

 selves. The remaining 

 figures more highly mag- 

 nified : 4, corpuscle seen on 

 its broad surface; 5, seen 

 on its edge ; 6, a series of 

 corpuscles ; 7, a corpuscle 

 in section, indicating its 

 biconcave discoidal form. 



