ACTION OF CYTOST 129 



out cytost showed no signs of growth, whereas those 

 made with the addition of cytost showed a satisfac- 

 tory growth, although, because of the lack of suitable 

 supporting structure, it was not so good as in controls 

 made with blood plasma. 



These experiments make it clear that even in such 

 an unfavorable environment as Locke's solution, cytost 

 may exert its growth-accelerating properties. Simi- 

 larly in such a medium cytost may, if its concentra- 

 tion be too high, exert a definite toxic action com- 

 parable to that found in the plasma cytost mixtures. 

 This was demonstrated experimentally by implant- 

 ing bits of actively growing cultures in a mixture of 

 one drop of Locke's solution and one drop of chick 

 cytost. Such cultures failed to grow, and unlike those 

 made in Locke's solution alone were found to be dead 

 after 48 hours' incubation. 



The lethal action upon tissue cultures of cytost in 

 high concentration is perhaps not of any especial sig- 

 nificance other than that it shows that a product of 

 cellular disintegration may be toxic to contiguous 

 normal cells — a fact in harmony with the numerous 

 experimental results quoted in preceding chapters, 

 which have shown that cytost introduced into the in- 

 tact animal or liberated in vivo by a localized injury 

 results in damage of the body cells, particularly those 

 of endodermal origin. On the other hand the stimula- 

 tion of cell growth by cytost is of very considerable 

 interest because a number of statements found in the 

 literature confirm the idea that cells influence the 

 growth of one another by the liberation of some sol- 

 uble substance. Thus, although many workers have 

 attempted to culture single cells in vitro they have 



