'). Aiitolijsis and hydrolysis of the proteins. 



Being neilhcr cncoiiiaijicd l)y llic (•\|)c'i-inu'nts iiu'nlioiicd 

 above nor !>> reading alxml tlic I'xperinients niade 



by H u r r () w s and N c y ni a n n '" in wiiicii llicy li-icd liie 

 elleel of amino acids on Ihe growlii of rii)robhists and lound, 

 thai they had a loxie action. I Iried. however, lo hy(h*o- 

 lyse the ])i"()leins ol' liic ciiiijryonic tissue juice. 1 tried 

 first to autolyse the tissue juice i)y keeping the tissue pulp 

 and the juice in the incubator at 39 C. for different lengths 

 of lime, from a few houi's lo several days. The result of 

 these expi'rinients was. that the extract being exposed to 

 the pulp at a temperature of 30" C. for a few hours lost 

 greatly in activity. By digesting the tissue pulp with trypsin, 

 no better results were obtained. 



I tried then to hydrolyse the proteins of the embryonic 

 tissue juice ad modum Kendall -^^ -^-), the method he 

 used to isolate the thyroxin. By this method I obtained 

 two fractions which Kendall called A and B. The frac 

 tion A was fatly and in consistency and colour like serumen. 

 This fraction could be brought into a kind of colloidal solu- 

 tion by boiling it with Ringer solution. The A fraction 

 showed little or no effect on the fibroblasts; if any a toxic. 

 The fraction B could easily be brought in a veritable 

 solution. This solution gave no precipitate with acetic acid. 

 Different concentrations of this B fraction were tried in 

 the cultures of fibroblasts. Solutions were made which con- 

 tained from 3,8 per cent and down to 0,05 per cent. A solution 

 containing 0,47 grams per hundred c. c. Ringer solution, 

 showed a slight activating power on the growth of fibro- 

 blasts. However, it did not have any toxic effect at all 

 on the growth of fibroblasts as stated by Burrows and 

 N e y m a n n *o). The amino nitrogen was determined in this 

 fraction after the method of Van Slyke ^^o) and found to 

 be 1 per cent. 



When it seemed that all these atlcmps to isolate a frac- 

 tion which was supposed to have a growth ])romoting power 



