76 



PROTOPLASM 



division (mitosis) takes place, with chromosomes clearly visible 

 (Fig. 57). It is believed that in certain types of cells (fibro- 

 blasts), division and multiplication do not take place if the cells 

 become fully isolated from each other. A single isolated cell in 

 culture does not multiply. Delicate intercellular connections 

 are usually visible and often very numerous (Fig. 60). 



1 .>«rs^ 





'ASf ■ 



%/ 



Fig. 61. — Drawing of human liver tissue in culture (culture supplied by Dr. 

 J. P. M, Vogelaar and drawn by Miss Ann Stiles). 



The types of tissues which have been grown in culture are 

 many. Practically all parts of the chick embryo— nerve, 

 epidermis, bone marrow, etc. — grow well. Cells of bone marrow 

 from adult organisms migrate very rapidly. Within an hour 

 after explantation they have spread over a large area. Other 

 tissues which have so far been cultured are the skin of the frog, 

 white blood corpuscles, tissues of rat, guinea pig, man, etc. 

 Human tissue has been successfully grown, though not extensively 

 so. Ebeling was one of the first (in 1914) to cultivate normal 

 and sarcomatous human tissue. Since then, several other 

 workers have experimented with similar cultures; thus, Castren 

 succeeded in keeping strains of fibroblasts obtained from a 



