CHICKEN BONE MARROW IN PLASMA MEDIUM 87 



which die, a large number 'steadily increase in size' and either 

 form cells of the macrolymphocytic type or of the large mono- 

 nuclear lymphocytic type, ''after the latter has undergone 

 nuclear enlargement and dechromatization." Foot presents no 

 dra^^^[ngs of these highly important forms, but considers it 

 sufficient to record the measurements of microlymphocytes of 

 different sizes, measuring from 3.5 to 9.6 in diameter. The 

 nuclear structure of these transition forms is not described by 

 him. The present author has never seen cells with typical 

 microlymphocytic condensed nuclei in all sizes, only cells with 

 vesicular achromatic nuclei in every possible size. In the later 

 discussion these contradictory reports of Foot and of the present 

 author must be borne in mind. 



Some authors hold the theory that microlymphocytes origin- 

 ated from the large mononuclear lymphocytes by multiple 

 simultaneous divisions. Only in very recently incubated tis- 

 sue cultures, as recorded on page 79 a breaking of large lymph- 

 ocytic forms into pieces was observed. But the isolated culti- 

 vating of these small cells afforded no definite results. Multinu- 

 cleated forms with ragged or torn cytoplasmic structure and 

 nuclei with highly condensed chromatin may be observed in 

 the case illustrated, of which three have a condensed chro- 

 matic structure (fig. 8). The younger the implanted bone mar- 

 row is, the more numerous these forms appear to be. They 

 have a slight resemblance in their plasma to very young connec- 

 tive tissue cells, as, e.g., Maximow ('10) pictures them in figure 

 43, from a guinea pig, but they seem to have no connection 

 with the formation of bone marrow lymphocytes. 



To summarize: The microlymphocyte belongs to those cell 

 types which undergo no progressive development in the tissue 

 culture. 



THE FATE OF THE IMPLANTED MYELOCYTES IN TISSUE CULTURES 

 OF CHICKEN BONE MARROW 



From the first to the sixth day after incubation large cell types 

 can be observed in the tissue culture of bone marrow when the 

 experiment is conducted with a full-grown, over a half year old 

 ehicken. These cell types have, as described on page 79, 



