143 



the tissues in the organism cerlainly did not meet wilh llie 

 best possible conditions of growth. If the blood was the 

 best possible medium, the cells would grow without restraint, 

 the organs and tissues would lose their relative size and 

 morphology, and the whole body would become monstrous. 



The variations of growth of certain tissues were then 

 studied in plasma, the conditions of which had been modified. 



It was discovered by L o e 1), in the growth of certain or- 

 ganisms that a slight alkalinity or hypotonicity increased 

 their growth considerably. The same sensitiveness was ob- 

 served by Carrel for living tissue cells in vitro. Modifi- 

 cations of the osmotic tension or the alkalinity, or the addi- 

 tion of certain inorganic salts to normal plasma, increase tlie 

 rate of growth of tissues. Ebelingi*'^) found that an 

 increase or decrease in the osmotic tension of the culture 

 medium at first stimulates cell proliferation, but eventually 

 retards it and proves to be unfavourable to growth. H o g u e 

 260) investigated the influence of various osmotic tensions 

 qualitatively on the tissue cells. 



In the fundamental experiments of J. Loeb on artificial 

 parthenogenesis, it was demonstrated that cell division can 

 be induced by slight changes in the composition of the sea- 

 water in which the sea-urchin's eggs are placed. It was 

 therefore supposed by Carrel ^^) that certain modifications 

 of the milieu i n t e r i e u r e of the tissues of mammals 

 would bring about the multiplication of their cells. Already 

 in 1907 — 08 Carrel studied the processes of reparation 

 of small cutaneous wounds and the action of various sub- 

 stances on the rate of cicatrization. It was obsei*\'ed that 

 the proliferation of epithelium and of connective tissues 

 was activated by dressing the wound with the pulp of tis- 

 sues and organs. Pulp of thyroid gland deposited on wounds 

 of the dog brought about the formation of exuberant granula- 

 tions. Applied to bones, it produced a marked thickening 

 of the periosteum. 



