162 



THE FLUIDS. 



well as that of the tissues. On the other hand, in leucaemia there 

 appears to be rather a general arrest of development of the white 

 corpuscles, and thus a great proportional diminution of the colored 

 ones. That the cytoid corpuscles of the blood are also liable to dis- 

 ease, especially to fatty degeneration, is a fact recently established 

 by the investigations of "Wedl and others. 



disks 



Fig. 97. 



B. The Colored Blood-corpuscles. 



The colored blood-corpuscles (red corpuscles, blood-cells, blood- 

 Fig. 97), which, in their natural or moist state, constitute 510 

 to 520 parts in 1,000 of blood, and 

 about one-half of its mass, are thick, 

 circular, slightly biconcave disks, ave- 



raging *A of an inch (Wuu to 3^, 

 Hassall) in diameter. Their thickness 

 at the circumference is about one-fifth 

 of their diameter. Their specific gra- 

 vity is 1088.5 to 1088.9 in men, and 

 1086 to 1088 in women. They consist 

 of a colorless cell-membrane, with red, 

 or, by transmitted light, yellow viscid contents. Some of them are 

 also originally found to contain one or more amorphous granules, 

 but none ever contain a nucleus. The corpuscles of the embryo 

 are somewhat larger than they are after birth. All the mammalia 

 have circular and discoid blood-corpuscles, except the camel, the 

 dromedary, and the lama, in which they are elliptical and biconvex. 

 In birds the corpuscles are long and oval, elevated in the centre, 

 and thick at the margin ; in the amphibia they are oval and very 

 convex. Those of most mammalia are smaller than those of man, 

 while those of the amphibia are far larger in some cases (the pro- 

 teus) ^Jfl of an inch in diameter. 



Colored blood-corpuscles. (Magnified 

 400 diameters.) 



The following are the mean dimensions of the blood -corpuscles of 

 several of the lower animals, compared with man (Schmidt) : 



Man . 

 Dog . 

 Babbit 

 Bat . 

 Pig 



Mouse 

 Ox . 

 Cat . 

 Horse 

 Sheep 



45^ 



Elephant . 

 Frog liyto 

 Siren . . 

 Proteus . 



It is evident that the blood-corpuscles and their viscid contents 

 must have a different composition from the intercellular fluid, or 



