I08 HOWELL. [Vol. IV. 



v/as the first to discover that in a number of animals, after 

 severe and repeated bleedings, the spleen again might contain 

 nucleated red corpuscles showing signs of active multiplica- 

 tion. This was denied by Neumann, who held that after such 

 an operation, the nucleated red corpuscles found in the spleen 

 were not more numerous than those present in the circulating 

 blood. But Bizzozero's observations have met with confirmation 

 at the hand of others, — Gibson (33), Foa (22), et al. ; and I also 

 in several cases have been able to show without any difficulty 

 that in the cat, after severe and repeated bleedings, and in some 

 cases after a single strong hemorrhage, nucleated red corpuscles 

 can be found in the spleen with every indication that they are 

 multiplying there. The balance of evidence is strongly in favor 

 of this power of the spleen to resume its embryonic function 

 when the demand for new red corpuscles is very urgent. In 

 what way severe anaemia stimulates the spleen to a renewal of 

 its haematopoietic actively is not known. It is very interesting 

 in this connection to find that, when the spleen of the adult 

 is partially excised, it is regenerated, and during the regenera- 

 tion not only nucleated red corpuscles, but giant cells are found 

 just as in the developing spleen of the embryo (Foa [42], 

 Tizzoni [43], Griffini [44]). It may be that in the adult spleen 

 a number of undifferentiated or erythroblastic cells are contained 

 which become aroused to activity in consequence of severe 

 anaemia, for the same reason, whatever it may be, that the cells 

 of the marrow are stimulated to increased growth and multipli- 

 cation by the same conditions-. 



Life-History of tJie White Corpuscles and Blood Plates, 



It is quite generally agreed that the origin of the white cor- 

 puscles of the blood is to be found in the lymph leucocytes, or 

 lymphocytes, to borrow a convenient term, which in turn are 

 formed in the lymphoid tissues of the body, and especially in 

 the so-called compound lymphatic glands. The lymphocytes 

 are characterized by a vesicular nucleus, usually with a nucle- 

 olus and a scanty reticulum, and by a very small protoplasmic 

 envelope. In the blood we meet with two chief varieties of 

 leucocytes, — uninucleated and multinucleated. The uninucle- 

 ated forms do not all have the same structure : some of them 



