426 



THE BLOOD 



[CH. XXVI. 



from the original formative cells of the embryo, or by the liver and 

 the other organs mentioned above, these coloured nucleated cells 

 begin very early in foetal life to be mingled with coloured non- 



o ^ 

 &.-. & 



-- 



Fm. 358. Part of the network of developing blood-vessels in the vascular area of a guinea-pig. U, 

 blood-corpuscles becoming free in an enlarged and hollovved-out part of the network; a, process of 

 protoplasm. (E. A. Schiifer.) 



nucleated corpuscles resembling those of the adult, and at about the 

 fourth or fifth month of embryonic existence are completely replaced 

 by them. 



Origin of the Matured Coloured Corpuscles. The non-nucleated 

 red corpuscles may possibly be derived from the nucleated, but in 



Fio. 359. Development of red corpuscles in connective tissue cells. From the subcutaneous tissue of 

 a new-born rat. h, a cell containing haemoglobin in a diffused form in the protoplasm ; h', one 

 containing coloured globules of varying size and vacuoles ; h", a cell filled with coloured globules of 

 nearly uniform size ; /, /, developing fat cells. (E. A. SchJifer.) 



all probability are an entirely new formation. Their chief origin 

 is: 



From the medulkt of "bone. It has been shown that coloured cor- 

 puscles are to a very large extent derived during adult life from the 

 large pale cells in the red marrow of bones, especially of the ribs. 

 These cells become coloured from the formation of haemoglobin chiefly 

 in one part of their protoplasm. This coloured part becomes separated 



