vI FORM AND FUNCTION 77 
The duty, almost the sole duty, of the red corpuscles, 
is to carry oxygen. It is the work of the colourless 
plasma to bring food to each part and to carry off the 
used-up material. The carbonic acid, which is pro- 
duced by the burning of the tissues, is probably 
removed, not by the corpuscles, but by the fluid 
in which they float. At the same time the plasma is 
busy with other work which falls mainly upon it, the 
work of carrying in all directions the food-materials 
which have entered the body, and thus what has 
been destroyed is rebuilt. It is probable that the 
various components of the blood divide their functions 
in the way I have described, but it is quite possible 
that further investigation may show that the foregoing 
account requires some modification. 
In what part of the body do the corpuscles originate ? 
In the lymphatic glands corpuscles very similar to, if 
not identical with, ordinary white corpuscles have 
been found in process of dividing into two. And it is 
thought that it is in these glands that the white or 
colourless kind are produced. 
In embryos, and, on occasion, in adults, the spleen, a 
small red body which can be found in birds attached to 
the right side of the fore-stomach (Proventriculus) 
certainly gives birth to many red corpuscles. In the 
marrow of human bones corpuscles are found inter- 
mediate in character between the white and the red, 
like the former possessing a nucleus, but like the 
latter having a little of the red hemoglobin, and these 
it seems are somehow transformed into ordinary red 
corpuscles. 
