43 



activation of tissue growth, it would he cxlrcmoly inloresling 

 and even practically usctul it such substances could i)c isola- 

 ted. Firstly, the mechanism of i^rowlli could be understood 

 and secoudly. processes of I'epair could be accelerated. As 

 Carrel ■"^) stated: -If the rale of the reparation of tissues 

 were activated ten tiuu's ouly. a cutaneous wound would 

 heal in less than twenty-four hours and a fraclui'e of the 

 leg would be cured in four or five days". 



As the experiment of C a r r e 1 showed, that healing of 

 the activating substances to .")<) C. diminished the activating 

 power and that even a fillralion through aBerkefeld 

 filter resulted in much less activating substances. I would 

 imagine that the questionable substances would be difficult 

 to isolate or separate on account of its lability. Although 

 there was only a slight h()i)e of getting hold of substances 

 or i)ortions of the tissue juice which had a still more 

 activating power on the growlli of tissues when separated 

 from certain indifferent or growth-inhibiting substances in 

 the tissue juice, it was worth while to undertake such 

 experiments in order to get some ideas or suggestions as to 

 the nature of those substances. 



A few investigators have already tried to cultivate tis- 

 sue cells in media with known composition. Lewis and 

 Lewis 337^3.00) Y\r^y^. ^^^^,^1 different salt solutions (sea- 

 water, Locke's solution and several modifications). As men- 

 tioned before, these inorganic solutions are not nourishing, 

 but protective, and consequently cannot be used as culture 

 media. O. Swezy i^") cultivated fibroblasts in culture me- 

 dia consisting of egg albumin and Ringer's solution. It has 

 not been possible to keep the tissue alive in those media for 

 any noticeable length of time. Burrows and C. A. N e y- 

 mann w) added to the i)lasma medium carbohydrates, fats, 

 ])eptones and'a-amino acids. They did not observe any 

 activation of the growth; on the contrary, it was observed 

 that 2—5 ])er cent peptones |)repared from the egg yolk 

 had no effect and the addition of a-amino acids on the 



