346 SPECIAL HISTOLOGY. 



and their dissolution, is not perhaps much slower than is com- 

 monly assumed, and whether they are not elementary parts of 

 a more stable nature than is supposed. I am unable to throw 

 any decided light upon this point, and will merely remark that 

 in any case, so long as the growth of the body goes on, and 

 the quantity of blood is augmented, an energetic formation of 

 blood-cells must take place; in opposition to which it is quite 

 unascertained whether, in this period of life, blood-cells are 

 dissolved; on which account, also, it cannot be stated how 

 many of the elements of the chyle undergo the metamorphosis 

 into blood-corpuscles. In the adult, only this much should be 

 regarded as certain, that when from any cause the quantity of 

 blood has become diminished, it may be replaced together with 

 the red blood-cells; whilst it is altogether unascertained 

 whether, under the usual conditions, anything like an energetic 

 solution and re-development of those cells takes place. As 

 their formation cannot be definitively observed, nothing remains 

 by which the question can be decided bin; observations respect- 

 ing the dissolution of the blood- globules; these observations, 

 however, have by no means tended to demonstrate the occur- 

 rence of a constant change of the elements of the blood, 

 taking place at short intervals; for although in the spleen of 

 many animals a vast quantity of blood-globules undergoing 

 disintegration is met with, the frequent and regular recurrence 

 of a dissolution of those bodies in that organ has not yet been 

 proved. Taking everything into consideration, I am therefore 

 of opinion, that the question as to when, and to what extent, 

 blood-corpuscles perish and are again formed in the adult, 

 cannot be definitively decided from the facts at present in our 

 possession, although I am inclined to think that the elements 

 of the blood are not altogether such perishable structures as is 

 commonly believed. 



I have still to mention, that, quite recently, the view that the 

 blood-globules are formed independently in the blood, out of 

 colourless cells, is advocated by various authorities. Lehmann 

 and Funke rely, the former on the large amount of colourless 

 cells in the blood of the hepatic veins, the latter on the similar 

 condition of the blood in the splenic vein, and they both con- 

 sider it probable, that a new formation of red blood-cells takes 

 place within the blood-vessels of the liver and spleen. It 



