38 WHITE CORPUSCLES. [BOOK i. 



though with less evidence, as taking place in the spleen, especially 

 under particular circumstances, such as after great loss of blood. 



The formation of red corpuscles is therefore a special process 

 taking place in special regions ; we have no satisfactory evidence 

 that the ordinary white corpuscles of the blood are, as they travel 

 in the current of the circulation, transformed into red corpuscles. 



The red corpuscles then, to sum up, are useful to the body on 

 account of the haemoglobin which constitutes so nearly the whole 

 of their solid matter. What functions the stroma may have besides 

 the mere so to speak mechanical one of holding the haemoglobin in 

 the form of a corpuscle, we do not know. The primary use of the 

 haemoglobin is to carry oxygen from the lungs to the tissues, and 

 it would appear that it is advantageous to the economy that the 

 haemoglobin should be as it were bottled up in corpuscles rather 

 than simply diffused through the plasma. How long a corpuscle 

 may live, fetching and carrying oxygen, we do not exactly know ; the 

 red corpuscles of one animal, e.g. a bird, injected into the vessels of 

 another, e.g. a mammal, disappear within a few days; fcut this affords 

 no measure of the life of a corpuscle in its own home. Eventually 

 however the red corpuscle dies, its place being supplied by a new 

 one. The haemoglobin set free from the dead corpuscles appears 

 to have a secondary use in forming the pigment of the bile and 

 possibly other pigments. 



The White or Colourless Corpuscles. 



28. The white corpuscles ate far, less numerous than the red; 

 a specimen of ordinary healthy blood will contain several hundred 

 red corpuscles to each white corpuscle, though the proportion, even 

 in health, varies considerably under different circumstances, ranging 

 from 1 in 300 to 1 in 700. But though less mftnerous, the white 

 corpuscles are probably of greater importance to the blood itself 

 than are the red corpuscles ; the latter are chiefly limited to the 

 special work of carrying oxygen from the lungs to the tissues, while 

 the former probably exert a considerable influence on the blood 

 plasma itself, and help to maintain it in a proper condition. 



When seen in a normal condition, and c at rest ' the white cor- 

 puscle is a small spherical colourless mass, varying in size, but 

 with an average diameter of about lOyu,, and presenting generally 

 a finely but sometimes a coarsely granular appearance. The surface 

 even when the corpuscle is perfectly at rest, is not absolutely smooth 

 and even but somewhat irregular, thereby contributing to the 

 granular appearance ; and at times these irregularities are exagger- 

 ated into protuberances or ' pseudopodia ' of varying size or form, 

 the corpuscle in this way assuming various forms without changing 

 its bulk, and by the assumption of a series of forms shifting its 

 place. Of these ' amoeboid movements ' as they are called we shall 

 have to speak later on. 



