142 HANDBOOK OF PHYSIOLOGY. 



other hand, claim an increase. The leucocytes are slightly increased 

 during menstruation. It is now the general opinion that pregnancy has 

 little or no effect on the number of red cells, and that any anaemia 

 must be due to abnormal conditions. Post-partum ansemia should not 

 last longer than two weeks. 



Varieties. The red corpuscles are not all alike. In almost every 

 specimen of blood a certain number of corpuscles smaller than the rest 

 may be observed. They are termed microcytes, or ImmatoUasts, and are 

 probably immature corpuscles. 



A peculiar property of the red corpuscles, which is exaggerated in 

 inflammatory blood, may be here again noticed, i.e., their great tendency 

 to adhere together in rolls or columns (rouleaux), like piles of coins, 

 These rolls quickly fasten together by their ends, and cluster; so that, 

 when the blood is spread out thinly on a glass, they form a kind of 



Fig. 118. Fig. 119. 



Fig. 118. Red corpuscles in rouleaux. The rounded corpuscles are white or uncolored. 

 Fig. 119. Corpuscles of the frog. The central mass consists of nucleated colored corpuscles. 

 The other corpuscles are two varieties of the colorless form. 



irregular network, with crowds of corpuscles at the several points cor- 

 responding with the knots of the net (fig. 118). Hence the clot formed 

 in such a thin layer of blood looks mottled with blotches of pink upon 

 a white ground, and in a larger quantity of blood such masses help, by 

 the consequent rapid subsidence of the corpuscles, in the formation of 

 the buffy coat already referred to. 



Action of Re-agents. Considerable light has been thrown on the physical 

 and chemical constitution of red blood-cells by studying the effects produced 

 by mechanical means and by various reagents : the following is a brief sum- 

 mary of these re-actions : 



Pressure. If the red blood-cells of a frog or man are gently squeezed, they 

 exhibit a wrinkling of the surface, which clearly indicates that there is a 

 superficial pellicle partly differentiated from the softer mass within ; again, if 

 a needle be rapidly drawn across a drop of blood, several corpuscles will be 

 found cut in two, but this is not accompanied by any escape of cell contents ; 

 the two halves, on the contrary, assume a rounded form, proving clearly that 

 the corpuscles are not mere membranous sacs with fluid contents like fat-cells. 



