No. I.] BLOOD CORPUSCLES. g^ 



tions of sections of the marrows of cats of all ages has not 

 revealed a separation of this character. On the contrary, the 

 erythroblasts seem to be scattered among the other elements 

 of the marrow without any apparent regularity. It is possible 

 that careful injection of the marrow will throw more light upon 

 the subject. On a priori ground, I should think that in the 

 mammalian marrow there must be some such arransreraent 

 as that described for the bird and the embryo, as it would 

 furnish the simplest explanation of the way in which the 

 newly formed red corpuscles develop and gain entrance into 

 the circulation, and would prove that the process of formation 

 in the adult and foetus and among the chief classes of verte- 

 brates is essentially the same. The embryonic cells from 

 which the erythroblasts are formed must also, of course, lie 

 in the unformed vessels with the erythroblasts, as is the case 

 in the embryo. 



Growth and Reproduction of tJie Nucleated Red Corpuscles. 



Since the observations of Bizzozero (19) it has been known 

 that the nucleated red corpuscles multiply by indirect division 

 (karyokinesis) like most of the other cells of the body. Though 

 his observations have not been disputed, other writers have 

 described different methods of growth, some of which have 

 been mentioned already. Foa and Salvioli (13) believe that 

 the nucleated red corpuscles are recruited continually from 

 the giant cells, Lowit (29) that they are developed from the 

 erythroblasts, and Malassez (27), Osier (28), and others take 

 a similar view. None of them, except Bizzozero, seem to lay 

 much stress upon the independent reproduction of the nucleated 

 red corpuscles themselves. It is quite easy to show, never- 

 theless, that Bizzozero' s observations are perfectly correct, and 

 that not only the erythroblasts, but the nucleated red corpus- 

 cles also, multiply by indirect division. Simple examination of 

 teased specimens of the marrow, especially of kittens which 

 have been bled severely, gives usually a number of corpuscles 

 undergoing division, such as are shown in Figs. 5 and 10. 

 Specimens teased in methyl green solution show sometimes a 

 portion of the spindle, as indicated in the figure ; but the chro- 

 matin filaments are not well preserved. The reagent seems 

 to swell the filaments into a mass, but, in spite of this, it is 



