16 



/. I'AXiporalion. 



'I'hv cxlracl \\;is placed in a thin layci" in w alcli-^lasscs 

 and c'vaporaU'd lo dryn<'ss. The e\a|)(»i ali(»n was done in dis- 

 sicalors under vacuum and conceiilialed sul|)huric acid or 

 calciimi chloi'ide. II look usually IVoni 'A lo ."> hours until 

 11 was ahsoluleiy dryed u|).* Il is. ol course, inipoi'lanl 

 that Ihe e\aporalion processes does not last Ioul; Ix-cause 

 the aclioii ol" sail concentration may harm the delicate sub- 

 stances. Tlie dry exti'acl was dissoh'cd in R i n f.( e i' solution 

 in dilTerenl concentr itions. Cullui'es with extract ol the 

 original, wliich had no! heen treated, served as controls for 

 the cultures to which these extract solidions were added. 



The result ol" these experimenls was, that the jfrowlh- 

 |)romolin<.; substances had lost greatly in actixity by the 

 eva|)oralion. even wlien the dry exti'acl was dissohcd in a 

 smaller (pianlity of li(|ui(l than that in svhich il originally 

 was dissolved. 



"2. Precipilalion c.vperimenls. 



I^xpei'iments were imderlaken lo isolate the dillei'cnt 

 globulins and albumins in llie tissue juice aftei- the well- 

 known chemical [)rincii)les and measure the power ol' ac- 

 tivation of the different fractions on cultures of fibroblasts. 



Ammonium s ii 1 p li a I e was used as a prccipilanl 

 in a series of experimenls. The extract was diluted equal 

 lo its own volume with Ring e r solution and half satura- 

 ted with (NIl4\.S()|. The solution was then centrifuged and 

 llu' pi'ecij)ilates washed with destilled water until the 

 ammonium sulphate was removed. The precipitates, which 

 represented the globulins, wei'c dissolved in a certain 

 amount of Ringer solution. This solution was added lo 

 the culture medium and the rate of growth of fibroblasts 

 determined. As controls served fibroblasts from the same 

 fragments as used in the culture of the experiment, but 



*) Quite recently, experiments of evaporating ttie embryo extract in a 

 very quiclt way (a few seconds) did not give any better results. 



