44 THE HUMAN BODY. 



and which, besides containing a store of new food matters 

 for the lymph, carries off the wastes which the various cells 

 have poured into the latter, and thus is also a sort of sewage 

 .stream into which the wastes of the whole Body are pri- 

 marily collected. 



Microscopic Characters of Blood. If a finger be 

 pricked, and the drop of blood flowing out be received on 

 -a glass slide, covered, protected from evaporation, and ex- 

 amined with a microscope magnifying about 400 diameters, 

 it will be seen to consist of innumerable solid bodies float- 

 ing in a liquid. The solid bodies are the blood corpuscles, 

 and the liquid is the Hood plasma or liquor sanguinis. 



The corpuscles are not all alike. While currents still 

 exist in the freshly spread drop of blood, the great majority 

 of them are readily carried to and fro; but a certain num- 

 ber more commonly stick to the glass and remain in one 

 place. The former are the red, the latter the pale or color- 

 less Uood corpuscles. 



Red Corpuscles. Form and Size. The red corpuscles as 

 they float about frequently seem to vary in form, but by a 

 little attention it can be made out that this appearance is 

 due to their turning round as they float, and so presenting 

 different aspects to view; just as a silver dollar presents a 

 different outline according as it is looked at from the front 

 or edgewise or in three-quarter profile. 



Sometimes the corpuscle (Fig. 10, B] appears circular; 

 then it is seen in full face; sometimes linear (C), and 

 slightly narrowed in the middle; sometimes oval, as the 

 dollar when half-way between a full and a side view. 

 These appearances show that each red corpuscle is a circu- 

 lar disk, slightly hollowed in the middle (or biconcave) and 

 about four times as wide as it is thick. The average trans- 

 verse diameter is 0.008 millimeter (-g-gVo inch). Shortly 

 after blood is drawn the corpuscles arrange themselves in 

 " rows, or rouleaux, adhering to one another by their broader 

 surfaces. Color. Seen singly each red corpuscle is of a 

 pale yellow color; it is only when collected in masses that 

 they appear red. The blood owes its red color to the great 

 numbers of these bodies in it; if it be spread out in a very 



