CHAPTER XXXVII.* 



THE CULTIVATION OF TISSUE " IN VITRO " AND ITS TECHNIQUE. 



1035. A culture of tissue consists of a special medium, natural or 

 artificial, such as lymph or plasma, inoculated with small fragments 

 of living tissues, and is characterised by an active growth of the cells 

 of the fragment into the nutrient plasmatic or lymph medium. 

 Cells wander out into the latter, and may live up to twenty days 

 without any signs of necrobiosis. 



The cultivation of tissues outside the body was first accomplished 

 successfully by Eoss Harrison, of Johns Hopkins University in the year 

 1907. This brilliant observer has demonstrated by a series of experi- 

 ments that fragments of nervous tissue of the frog embryo, covered with 

 fluid from the lymph sac of an adult frog, show growth of long nerve 

 fibres (HARRISON, Proc. Soc. Exper. Biol. and Med., iv, 1907, p. 140). 

 Alexis Carrel, at about the same time, had been studying the laws of 

 redintegration of tissues, and adapted Harrison's technique to mam- 

 malian tissues. M. Burrows, a pupil of Ross Harrison, at this period 

 began to work on tissue -culture, and first used blood plasma instead of 

 lymph. Subsequently Burrows adapted the technique of Harrison to 

 the cultivation of tissues of the chick. In September, 1910, Carrel and 

 Burrows, working in conjunction at the Rockefeller Institute, succeeded 

 in cultivating, in vitro, the adult tissues of mammals, and thus began a 

 series of contributions which have taught us many valuable facts 

 regarding senesence and rejuvenescence and the pathology of tissues 

 (CARREL and BURROWS, Jour. Exper. Med., xiii, No. 3, 1911). 



Two methods of tissue-culture may be distinguished : 



(1) Hanging-drop or smear cultures (Harrison). 



(2) Large plate cultures (Carrel and Burrows). 



The former are useful for direct observation of living growing 

 cells, the latter can be studied when fixed and cut into sections. 



There has been a great deal of work done on tissue-culture, but 

 most of it has been carried out by vertebrate pathologists and 

 histologists. There seems little doubt that this field is a most 

 promising one for zoologists as well as histologists. Many problems 

 of gametogenesis and general cytology might be settled by recourse 

 to tissue-culture, especially by the application of such methods to 

 the cells of invertebrate animals, whose cytology had previously 

 been examined in detail with the aid of modern techniques. 



* By J. B. G. 



