1 1 



The inriiuMicc ol' cxlnicls IVom vjirioiis lissiics \v;is Iricd 

 on llir is()l;il('(l lissiu- ci'lls in xilro. I-^xIimcIs ol" cliickm em- 

 bryos, ol' spleen, kidney, nuiseies, i{ o ii s sarcoma. Ilivroid 

 f^land weiH made and added lo llie plasma medium ol' [lie 

 tissue cells and the exleiil ol' iji-owlh measuicd Tlie resulls 

 ohiained al llial time, when llie lechnicpie ioi- (issue cul- 

 li\ation was nol as perl'ecl as il is now. were ralhei' slrikin<>'. 

 All Ihe lissuc extracts were found to activate f^i'owlh ol' ttie 

 connective tissue, but the decree of acti\ation \aried mucli. 

 I^ml)rv()nic tissue juice was the most actiNc. l-]xlracls of 

 adult spleen and tlie Ho us sarcoma wci-e almost as aclivo 

 as tlie extract of cliicken eml)i'yos. Kidney and lieaiM extracts 

 were mucli less actix'e. wliile the extracts of connect i\e 

 tissue and of l)l()o(l coi'puscles l)rou.ii;lil about a sli<«lil ac- 

 celeration only of the growth. The influence of the tnyroid 

 f*land extract and the muscle of tlie do^f on the frrowlh of 

 periosteum was very marked. Thyroid extract was moi'e 

 active tlian muscle extract. It was also obserNcd that when 

 the extracts were heated to .">() (]. foi- from 10 minutes to 

 half an hour tliey almost lost their activity, l-'ilti-ation of llu' 

 extracts throuffli Berkefeld filter, caused a considcral)le 

 decrease in the activity of them, and filtration thi"ou<j;h a 

 Cham her land filler suppressed completely the activating 

 power of an extract. This has already been mentioned in the 

 chapter on the culture media. 



It was learned as a fact, that the tissue cells are able 

 to live for a short time in plasma alone; and that the death 

 of the tissues could be i)i-evented by adding small amounts 

 of extracts from chicken embryos. The j^lasma did nol 

 contain the substances necessary for the indefinite mnltipli- 

 cation of iibi-oblasts. Although the fibroblasts cannot live 

 indefinitely in jjlasma. they often gi-ow with a great activity 

 for several weeks. According to L e w i s ■'•^'^). I n g e b r i g l- 

 sen-*^^; and H n r r o w s •^'~) *"i the tissues grow al the ex- 

 pense of tlie food stoi'ed up in the bodies of the cells. 

 Therefore an actual increase of the l)ulk of the tissue was 



