DEVELOPMENT OF THE BLOOD CORPUSCLES. 421 



be regenerated in large numbers in the blood of adult animals, 

 and this is accomplished at the expense of the white corpuscles, 

 as was demonstrated in the case of the frog by V. Reckling- 

 hausen, and still more recently again by Golubew. Fission of 

 the red blood corpuscles in adult animals has only been observed 

 in a few rare instances. 



Whether the colourless corpuscles always undergo multipli- 

 cation within the blood itself, and by what mode of cell genesis 

 they multiply, are still open questions. It is certain that a 

 large number of white corpuscles are added to the blood, not 

 only during the period of development and of growth of the 

 animal organism, but also throughout life, by the agency of the 

 lymph current, the corpuscles of this current originating in 

 localized germ-producing organs, situated external to the blood 

 (lymphatic glands). 



If the continual addition of such young cells had only as an 

 object the supply of material for the regeneration of the red 

 blood corpuscles, it would demonstrate that the latter are very 

 unstable structures, structures in which rapid metamorphoses 

 take place. Independently, however, of the circumstance that 

 it is possible the white corpuscles themselves undergo disinte- 

 gration in the blood, we know as a fact that they migrate from 

 the interior of the vessels into the tissues, and that they par- 

 ticipate in effecting certain plastic processes in these tissues,; 

 on the other hand, up to the present time we are acquainted 

 with only two regularly recurring processes, in one of which 

 menstruation there certainly occurs, whilst in the other the 

 preparation of bile* there very probably occurs the destruction 

 of a large number of red blood corpuscles. 



Moreover, the observations on the disintegration of the red 

 blood corpuscles may here be alluded to, that have been de- 

 scribed as taking place in the formation of pigment in the 

 spleen, in the blood-corpuscle-holding cells of the spleen (vide 

 spleen), and of the medulla of the bones ; but in regard to the 

 period* of the occurrence of which during life nothing is at 

 present known. 



* Kiihne, Physiologische Chemie, p. 88. 



