105 



and inulliply, and finally art" ()l)lained pure. The same 

 method is used in geltinjf (he l)i^ mononuclear lymphocytes. 

 When leucocytes are cultivated, all the different elements of 

 cells will die out excei)t the hig mononuclear lymphocytes, 

 which will ])ersisl, (C a r r e 1 and E b e 1 i n g ^^;. The method 

 is somewhat similar to the different elective methods for 

 obtaining pure cultures of certain bacteria, as for instance, 

 the diphtheria bacilli by cultivation on serum, the typhoid 

 bacilli by the Inle method, and so on. The horse serum or 

 the bile is not used because dij)htheria bacilli grow better 

 in horse serum, or typhoid Ijacilli grow better in bile, but 

 because other bacteria grow very poorly on these substances. 

 The same thing is probably the case with epithelial cells, 

 polymorphonuclear leucocytes, and so on; they do not grow 

 so well under the same conditions as the fibroblasts. 



The other method for obtaining pure cells for cultivation, 

 the anatomical, is simply done by dissecting the pure tis- 

 sues out from the organism. The tissue cells for cultivation 

 have to be taken from certain anatomical loci elecli, where 

 we know that these tissues are pure, i. e., only contain one 

 type of cells. Rather few tissues are pure. The majority of 

 them are complex, containing ameboid cells, vessels, glands 

 with their various cell elements. Cartilage is a tissue which 

 can be obtained pure that way. Epithelium is more difficult 

 to obtain because it is often so closely adherent to the 

 endothelial and connective tissue cells; nevertheless it is 

 rendered possible to obtain pure epithelium, from certain 

 loci elecli. 



FIHROBLA.STS. 



The connective tissue strain which has been cultivated 

 for more than 12 years in the Rockefeller Insti- 

 tute in New York. (Fig. 8). and for 3 years in the 

 Institute of General Pathology of Copenha- 

 gen were isolated from a complex tissue, namely a piece 

 of embryonic heart After a certain length of cultiva- 



