534 FORMATION OF RED BLOOD CELLS. |_SECT. 222. 



to be distinguished from true red blood-corpuscles, except by their 

 slightly granular appearance. In this situation, too, the pale 

 blood-cells showed somewhat smaller nuclei than elsewhere; but 

 even this point is not conclusive. We may, however, adduce, as 

 very important analogies in favour of this hypothesis, I. that in all 

 the lower vertebrata, even in the adult animals, the origin of the 

 nucleated blood-cells from the lymph-corpuscles may be very dis- 

 tinctly observed ; this is seen most plainly in the amphibia : and 2. 

 that even in the human embryo, and in the spleen of the newborn 

 child, the formation of the coloured blood-globules from colourless 

 cells very similar to the lymph-corpuscles, has been demonstrated 

 most definitely. When, moreover, it is considered, that nothing is 

 known of an independent multiplication, or any other mode of origin 

 of the blood-cells, I feel justified in expressing my opinion, that the 

 red blood-cells take their origin from the lymph-corpuscles; and I 

 would further venture to suggest, that the reason why the transition 

 has never been observed is, that it takes place too quickly to be at 

 all followed by the methods of observation which we can employ. 



Although, in the foregoing, I have expressed myself in favour of 

 the formation of the red blood-cells from the elements of the lymph 

 and of the chyle, I do not by any means intend to assert that all 

 the elements of these juices are transformed into blood-cells at all 

 periods of post-embryonic life. The microscopical examination of 

 the blood shows, indeed, that a certain number of large pale cells 

 (with several . nuclei, or with one nucleus which breaks up on the 

 addition of acetic acid) are invariably present in fully-formed 

 blood; and it appears impossible to suppose that these ever become 

 red blood -corpuscles, although they certainly come from the chyle, 

 or else are metamorphosed elements of it ( Virchow and myself). 

 If this be established, the question arises, whether the change of 

 the blood-cells, their formation, and their decay, may not follow 

 much more slowly than is usually assumed, and whether the pale 

 corpuscles may not be much more stable elementary parts than has 

 been hitherto supposed. I cannot give any definite explanation on 

 this point, and will only remark, that in any case, as long as the 

 body grows and the volume of the blood increases, an energetic 

 formation of blood-cells must certainly be going on ; on the other 

 hand, it is wholly undetermined whether the blood-cells at this 

 period of life undergo any process of solution, and on this account, 

 therefore, we are unable to estimate what proportion of the 

 elements of the chyle undergoes transformation into blood-cor- 

 puscles. In the adult, only this much, perhaps, is quite certain, 



