98 ANATOMY FOR NURSES. [CHAP. VIII. 



absorbing the water causes the corpuscles to shrink, and become 

 wrinkled or crenated. The red corpuscles are practically small 

 flattened bags, or sacs, the form of which may be changed by 

 altering the density of the plasma. They are very soft, flexible, 

 and elastic, so that they are readily squeezed through apertures 

 and passages narrower than their own diameters, and when 

 pressure is withdrawn, immediately resume their proper shape. 



Function of the red corpuscles. The red corpuscles, or ery- 

 throcytes, by virtue of the haemoglobin which they contain, are 

 emphatically oxygen carriers. Exposed to the air in the lungs, 

 the haemoglobin combines with the oxygen present in the air ; 

 this oxygen the haemoglobin carries to the tissues ; these, more 

 greedy of oxygen than haemoglobin itself, rob it of its charge, 

 and the haemoglobin, thus deprived of its oxygen, hurries back 

 to the lungs for a fresh supply. 1 The utility of the haemo- 

 globin consists in the ease with which under certain conditions 

 (those existing in the lungs) it takes up oxygen, and the 

 readiness with which under certain conditions (those existing 

 in the capillaries) it gives up this oxygen again. The colour 

 of the blood is dependent upon this combination of the 

 haemoglobin with oxygen; when the haemoglobin has its full 

 complement of oxygen, the blood has a bright red hue ; when 

 the amount is decreased, it changes to a dark purplish hue. 

 The scarlet blood is usually found in the arteries, and is 

 called arterial; the dark purple in the veins, and is called 

 venous blood. 



White corpuscles of the blood. The white, colourless corpus- 

 cles, or leucocytes, are few in number compared with the red, 

 and both on this account, and because of their want of colour, 

 they are not at first easily recognized in a microscopic prepara- 

 tion of blood. Their form is very various, but when the blood 

 is first drawn they are rounded or spheroidal. Measured in 

 this condition they are about ^-g^ of an inch (0.010 mm.) 

 in diameter. The white corpuscle may be taken as the type of 

 a free animal cell. It is a small piece of protoplasm, contain- 

 ing a nucleus, and has no limiting membrane or cell-wall (vide 



Fig. 77, F,ay. 



These corpuscles, or cells, possess the power of spontaneous 



1 Processes which are characterized by combination with oxygen are known 

 as oxidation, while the reverse processes are known as reduction. 



