CHAPTER VII 



TISSUE-CULTURE IN VITRO 



Chapter I demonstrated the fundamental differences existing 

 between classical cytology, a science of pure observation which 

 suppresses evolution in time by killing the cells, and what 

 Carrel calls *the new cytology'. This new experimental science 

 enables the searcher to consider the cells in their environment 

 and to observe the reactions determined by modifications in 

 the surrounding medium, as a function of time. To make a 

 comparison, the classical cytology corresponds to the dissec- 

 tion of corpses, whereas tissue-culture is related to medicine, 

 physiology and, one might even say, to elementary sociology. 

 Taken in a restricted sense, this expression is not exaggerated. 

 Indeed, cinematographic films of cell-cultures have revealed 

 totally unknown and unforeseen facts related to the behaviour 

 of the free cells such as the leucocytes (white cells of the blood) 

 and macrophages. These cells, instead of living in a consistent 

 mass, bound one to another Hke the tissue-cells, disseminate 

 themselves in the culture-medium 'like children let loose in a 

 school -yard'. The pictures are taken, dccording to the 

 activity of the culture, every lo, 15, 20, or 30 seconds, during 

 periods varying from 24 to 72 hours. They are projected at 

 the ordinary rate of 16 per second or less. Every motion of 

 the cells is therefore considerably accelerated (from 160 to 

 500 times or more). It is thus possible to discern unsuspected 

 movements and mutual reactions, otherwise imperceptible, just 

 as in the well-known films which revealed to us the opening 

 of a bud and the blossoming of flowers. Unleashed leucocytes 

 can be observed attacking a nervous fibre which resembles 

 a taut string. The fragile and tenuous fibre is bent by the 

 shocks like the string of a bow in the hand of an archer. One 

 sees the macrophages in blood-plasma surrounding themselves 

 with a large undulating membrane resembling a sequence of 

 wavelets in a calm sea at low tide when they die without 



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