DESTRUCTION OF RED BLOOD-CORPUSCLES. 43 



borne in mind that Schafer observed similar formative processes in the 

 subcutaneous connective tissue of young rats, the question must arise 

 whether such blood-forming stations do not exist in many parts of the 

 body and constitute seats for the regeneration of the blood. 



For purposes of demonstration it is only necessary to observe omentum of 

 suitable age in a fresh state in peritoneal fluid, evaporation being prevented by 

 applying paraffin to the edges of the cover-glass. Landois saw preparations of 

 this highly interesting developmental process in the laboratory of Ranvier at 

 Paris with such a degree of distinctness as to leave in his mind no doubt as to 

 the accuracy of the observation. Neumann saw analogous formations in the 

 embryonal liver, Wissotzky in the amnion of the rabbit, Nicolaides in the mesen- 

 tery of the guinea-pig, Klein in the amniotic sac of the chicken's egg, Bayerl in 

 the cartilaginous capsules of ossifying cartilage, Leboucq and Hayem in other 

 situations, all indicative of the fact that the blood-cells develop endogenously 

 in certain cellular structures of considerable size whose protoplasm serves at the 

 same time for the formation of the vessel-wall. 



C. At a later period of life the red blood-corpuscles develop from 

 special nucleated cells, the erythroblasts. It is believed that the latter 

 gradually assume the form and color of perfect erythrocytes. Accord- 

 ing to Neumann they possess blood coloring-matter from the outset. 

 In caudate amphibia and fish the spleen, and in all other vertebrates, 

 the bone-marrow constitutes the seat for the formation of those juve- 

 nile forms that multiply by division. Particularly in the latter all stages 

 of the transformation may be seen, especially pale, contractile cells 

 resembling white blood-corpuscles, and later on red nucleated corpuscles 

 that must be considered as the progenitors of the red corpuscles and 

 that are capable of undergoing multiplication by mitosis. 



After copious loss of blood the process of transformation and the 

 entrance into the blood-stream is said to be observed in especially 

 marked degree. J. Arnold found in the protoplasm of the nucleated 

 erythrocytes of bone-marrow granules resembling those of hemo- 

 globin-free cells. In the process of transformation into red blood- 

 corpuscles these granules become invisible through transformation. 

 The products of the mitotic division of the pale cells especially are to 

 be considered as the progenitors of the nucleated erythrocytes. In the 

 red bone-marrow, perhaps also in the spleen, the small veins and most 

 of the capillaries have no definite wall. The formed erythrocytes accord- 

 ingly can at any time be swept into the circulation from these parts. 



The bones of the skull and most of those of the trunk contain red (blood- 

 forming) marrow, while the extremities contain only fatty marrow, or only the 

 upper portions of the femur and the humerus contain red marrow. When active 

 regenerative processes are taking place in the blood the fatty marrow may be 

 transformed into red marrow, and indeed from the upper portion of the bones 

 named downward, even through all the bones of the extremities. Red, blood- 

 corpuscle-forming marrow may develop even in the ossitk-d laryngeal cartilages 

 and in pathological bony tumors. 



DESTRUCTION OF RED BLOOD-CORPUSCLES. 



As erythrocytes are being constantly formed, it must be assumed 

 that they are being constantly destroyed. Further, the situations are 

 known in which this occurs especially. Among these is first the liver, 

 as the elements of the bile are formed from blood coloring-matter 

 and the blood of the hepatic veins contains a smaller number of red 

 blood-corpuscles. The splenic pulp also contains cells indicative of 



