38 WHITE CORPUSCLES. [BOOK i. 



A similar formation of red corpuscles has also been described, 

 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 ; 

 but 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 are 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 numerous, 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 ' at rest ' the white 

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

 with an average diameter of about 10 /-t, and presenting in some 

 cases a finely granular or even hyaline, in others a coarsely granular 

 appearance. The surface, even when the corpuscle is quite spheri- 

 cal, is not always absolutely smooth but may be somewhat irregular, 

 thereby contributing to the granular appearance; and at times 

 these irregularities are exaggerated into protuberances or 'pseudo- 

 podia ' of varying size or form, the corpuscle in this way assuming 

 various forms without changing its bulk, and by the assumption 



