ORIGIN OF THE RED BLOOD-CORPUSCLES. 



are very rarely found. Of course, in animals with nucleated blood-corpuscles, the 

 nucleus of the embryonic blood-corpuscles remains. 



(B) During Post-Embryonic Life. Kolliker assumed that in the tail of the tadpole 

 capillaries are formed by the anastomoses of the processes of branched and radiating 

 connective-tissue corpuscles. These corpuscles lose their nuclei and protoplasm, 

 become hollowed out, join with neighbouring capillaries, and thus form new blood- 

 channels. J. Arnold and Golubew oppose this view, asserting that the blood- 

 capillaries in the tail of the tadpole give off solid buds at different places, which 

 grow more and more into the surrounding tissues, and anastomose with each other ; 

 after their protoplasm and contents disappear they become hollow, and a branched 

 system of capillaries is formed in the tissues. Ranvier noticed the same mode of 

 growth in the omentum of newly-born kittens. 



Young rabbits, a week old, have, in their omentum, small white or milk spots 

 {Ranvier), in which lie " vaso-formative cells," i.e., highly refractive cells of 

 variable shape, with long cylindrical protoplasmic processes (fig. 8). In its refractive 

 power the protoplasm of these 

 cells resembles that of lymph- 

 corpuscles. Long rod-like nuclei 

 lie within these cells (K, K), and 

 also red blood-corpuscles (r, r), 

 and both are surrounded with 

 protoplasm. These vaso-forma- 

 tive cells give off protoplasmic 

 processes (a, a), some of which 

 end free, while others form a 

 network. Here and there elon- 

 gated connective-tissue corpuscles 

 lie on the branches, and ulti- 

 mately form the adventitia of the 

 blood-vessel. The vaso-formative Formation of red blood- corpuscles within "vaso-forma 



cells have many forms : they may 

 be elongated cylinders ending in 

 points, or more round and oval, 

 resembling lymph cells, or modi- 

 fied connective- tissue corpuscles. 



tive cells, " from the omentum of a rabbit seven 

 days old. r, r, the (brined corpuscles ; K, K, nuclei 

 of the vaso-formative cell ; a, a, processes which 

 ultimately unite to form capillaries. 



These cells are always the seat of origin of non- 

 nucleated red blood-corpuscles, which arise in the protoplasm of vaso-formative cells, 

 as chlorophyll grains or starch granules arise within the cells of plants. The 

 corpuscles escape, and are washed into the circulation when the cells, by means of 

 their processes, form connections with the circulatory system. Probably the vessels 

 so formed in the omentum are only temporary. May it not be that there are many 

 other situations in the body where blood is regenerated 1 



[The observations of Schafer also prove the intra-cellular origin of red blood - 

 corpuscles, and although this mode usually ceases before birth, still it is found in 

 the rat at birth. The protoplasm of the subcutaneous connective-tissue corpuscles, 

 which are derived from the mesoblast, has in it small coloured globules about the 

 size of a coloured corpuscle. The mother-cells elongate, become pointed at their 

 ends, and unite with processes from adjoining cells. The cells become vacuolated ; 

 fluid or plasma, in which the liberated corpuscles float, appears in their interior, and 

 ultimately a communication is established with the general circulation.] 



Neumann observed similar formations .in the embryonic liver ; Wissotzky in the rabbit's 

 amnion ; Klein in the embryo chick ; and Bayerl in ossifying cartilage. All these observations 

 go to show that at a certain early period of development blood-corpuscles are formed within 

 other large cells of the mesoblast, and that part of the protoplasm of these blood-forming cells 

 remains to form the wall of the future blood-vessel. 



