iv THE BLOOD: FOKMED CONSTITUENTS 101 



according to their form and size (distinctions which concern the 

 pathologist) into normal erythrocytes, micro- and macrocytes, 

 and poikilocytes (pear-shaped, rod -shaped, etc.). Again there 

 are red corpuscles which exhibit granules of different si/es and 

 shapes in their protoplasm, and which will stain with all the 

 basic dyes (basophile granulation). On changing the stains, the 

 figures produced assume quite different forms ; this shows that 

 the figures that we see do not correspond exactly with the pre- 

 existing arrangement of the chromatic substance, but depend on 

 the different physico-chemical actions exercised by each individual 

 colouring substance (Cesaris Demel). The significance of these 

 granules is uncertain ; by some they are considered to be the 

 remains of nuclei, according to others they are protoplasmic 

 formations. 



FIG. 27. Red blood-corpuscles of man. (Magnification, 650 diameters.) Some are seen flat, others 

 in profile, the majority are disposed in rouleaux. 



Although Schultze has described active movements of the 

 protoplasm in the nucleated erythrocytes of the chick, it is very 

 doubtful whether the red corpuscles of mammalia are capable of 

 expanding and contracting in the medium in which they normally 

 live. When, however, they are taken out of the vessels, and cooled 

 or warmed, or excited by induction shocks ; when the degree of 

 concentration of the plasma in which they float is altered by the 

 addition of water or of saline solutions ; when they are brought in 

 contact with extraneous chemicals, they readily change their shape, 

 assuming a mulberry-like or even prickly (crenate) appearance, 

 and extending or retracting different segments of their protoplasm, 

 as if undergoing amoeboid movements. The former changes are 

 the effect of altered osmotic conditions, the latter are probably 

 to be regarded as active movements (Figs. 28 and 29). 



The capacity of erythrocytes for active movements in certain 

 special abnormal conditions is confirmed by the observations of 

 A. Cavazzani. He noticed that when blood was collected in an 

 isotonic or hypotonic solution of sodium chloride, to which potassium 



