181) 



unconlrolk'd <*r()\vth froni the l)t'ginning, in spile of llie 

 fad, thai such tragmenls oT inlesline conlain at Icasl Iwo 

 injured ends. 



Rather hllle is known ol' (he inleracLion of the vaiious 

 tissues. II is of great importance to know about (he laws 

 wliich control the rate of proliferation and the limits of mi- 

 gration of the various tissues; in other words it is iui- 

 porlanl to investigate the cori'elalion of llie tissues, in order 

 to understand a little about the numerous pathological pro- 

 cesses. 



In a previous chapter, we have described a factor which 

 plays an important role for the multiplication of the tis- 

 sue cells. It was observed that single isolated cells are not 

 able to divide and multiply, unless in direct protoplasmic 

 relation to other cells of the same kind. It was also ob- 

 served, that the stimulus regulating the simultaneous con- 

 traction of a heart fragment, is transported from one cell 

 to another through the protoplasmic anastomosis of the 

 muscle cells. 11 was found, that the stimuli leading to the 

 simultaneous contraction of the fragment, were blocked by 

 the interposition of fibroblasts. 



This fact leads us to assume, that specific impulses are 

 not transported from cells of one type to cells of another. 

 This assumption may probably be true also as regards the 

 growth stimulating factors, transported from cells of one 

 kind to cells of another. In other words, a single epithelial cell 

 may not impart to a single fibroblast the stimulus for cell 

 division. It was found by other investigators, that protoplas- 

 mic connections between epithelial cells and fibroblasts 

 were not seen in the organism. These phenomena are still 

 unknown, but investigations have already commenced. If it 

 be true, that the stimuli inducing the cell division, are specific 

 for the various cell types, we should be able to understand 

 a good deal more of regeneration, transplantation and other 

 related processes. 



Many unknown factors of the transplantation may be ex- 

 plained that way. The reason why homologous and heterolog- 



