201 



llic riinclion of iiourisliiiij^ lissiics. besides IIkiI of disiiiU-- 

 graling forei.^n subslanccs. ncci'olic cells. l);icleri;i a. s. o. 



Accordinj* lo llieir ('(nidilion, leiieocyles lil)erale suhslaii- 

 ces ol" varied nature, (replioiies ai"e secreled by normal cells, 

 or diri'iise tVom dead cells before lliey disinlcj^rale. Tre- 

 pliones i)rol)ably (lisai)|)ear al a certain statue of cell dcf»ene- 

 ration. according to Carrel, and tlie substances which dif- 

 fuse fi-oni disintegrating leucocytes are often toxic for tlie 

 tissue cells, r^xtracl from pus genei"ally depi-esses (he mul- 

 tiplication of cells. (> arret has observed in vivo, that the 

 cicati'ization of woiuids is delayed when an abscess in some 

 pari of (he body is pi'esenl. Similar obserNalions were made 

 when sterile pus was injected sid)cutaneously while liie 

 healing of the wound was observed. 



According lo Carrel ])athological processes are often 

 charactei'ized by a reactivation of tissues which possibly for 

 many years have ceased lo multii)ly. There has always 

 been a cpieslion as to what determines an increase of Ihc 

 growth enei'gy of a tissue when it is needed. P'rom (he ex- 

 periments of Carrel we have learned thai Ihe growlh 

 energy depends on substances that arc present in the peri- 

 cellular fluid and not on the energy derived from the ovum. 

 As long as the cells are sujiplied wnth these siil)slances, 

 they exhibit an unlimited ])ower of proliferation. The peri- 

 cellular fluid of the adidt organism does not contain growth- 

 promoting substances in any noteworthy quantity. 11 is 

 shown recently by Riser*), that adult tissue cells and fibro- 

 blasts have the powa^r of unlimited multiplication in vitro, 

 when cultivated in media containing embryonic tissue juice. 

 The tissue cells from the adult organism are able lo produce 

 unlimited amounts of living pr()to|)lasm when they are fed 

 on embrj^onic tissue juice. In case of jiathological processes^ 

 trephones are secreted by leucocytes or set free by dead 

 muscle or gland tissue. As soon as the concentration of tre- 



*) Personal communication. 



