36 FORMATION OF RED CORPUSCLES. [BOOK L 



red corpuscles, pass away into the general blood current. In other 

 words, a formation of red corpuscles, not wholly unlike that which 

 takes place in the embryo, is in the adult continually going on in 

 the red marrow of the bones. 



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, rang- 

 ing 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. 



The white corpuscle, which is often taken as the type of ' a 

 cell,' consists of a cell-body or cell-substance and a nucleus. 

 Several varieties or kinds of white corpuscle are found in the 

 blood, differing from each other as to size, as to the characters of 

 the nucleus, as to the characters of the cell-substance, as to the 

 extent to which they exhibit ' amoeboid ' movements, whereby 



