TISSUE-CULTURE IN VITRO II3 



the normal conditions in the organism. But its activity 

 manifests itself in other ways. The cells function physiologi- 

 cally. Instead of proliferating rapidly they accompUsh the 

 tasks which they fill in the organism and begin to secrete the 

 substances which they produce normally. In my laboratory 

 at the Pasteur Institute where a pure Uver-culture had been 

 isolated (Doljansky) it had been noticed that the well-fed cells 

 no longer manufactured 'glycogene', a substance which 

 transforms itself into sugar (glucose) and is one of the most 

 important products normally elaborated by this organ. When, 

 however, the culture had been submitted to a reduced diet 

 by the suppression of the embryo juice, the glycogenic func- 

 tions started working again exactly as in the organism. The 

 same phenomenon was observed with the pigment cells of 

 the iris. When too well nourished, the cells proliferate 

 abundandy but without producing any pigment or colouring 

 matter. When dieted, they cease growing in number, but 

 secrete the black pigment which characterizes them in vivo. 



It is evident that this method is particularly adapted to the 

 study of cancer. It suffices to compare pure cultures pro- 

 ceeding from malignant cells to cells of the same type but 

 devoid of malignancy. It was thus soon ascertained that 

 macrophages proceeding from Rous sarcoma are unhealthy 

 abnormal cells which degenerate rapidly and do not Uve long. 

 They require the same nourishment as normal macrophages, 

 but unlike the latter they actively digest the coagulum. The 

 fibroblasts proceeding from another tumour, the 'Crocker no. 

 10' are, on the other hand, strong and healthy, require the same 

 nourishment as normal fibroblasts, but also digest the coagulum. 

 Epithelial cells from the Ehrlich carcinoma are unhealthy and 

 delicate cells like those of the Rous sarcoma. They likewise 

 digest the coagulum. 



Other types of malignant cells have been studied, and it 

 was found that no matter how divergent they are on certain 

 points they all have properties in common, such as this faculty 

 of digesting and liquefying the solid part of the coagulum, the 

 fibrin. Furthermore, they can assimilate substances which do 



