338 Tumors. 



displacements and isolations of osteoblasts, cartilage tissue or 

 epithelium, as causative of the autoblastomatous new formations. 

 It is not rare to see connective tissue proliferations of considerable 

 extent, completely reproducing the characteristics of fibromata, 

 developing from injuries of the tendon sheaths (horse and cow) 

 or of the tongue (cow) ; the growth is apparently the product of 

 a chronic inflammatory^ process and the result of an excessive 

 growth of granulation tissue. \Miether some special irritant, 

 perhaps bacteria, bring about such tumor-like formations, 

 whether absence of tissue tension occasioned by the trauma is 

 the single or principal reason for its occurrence, remains an 

 open question. At all events it is recognized that there are no 

 sharp lines of difference between tumors and regenerative prolif- 

 erations, and that the hypertrophies, which are regarded as sim- 

 ple proliferations in vacuo (as of liver) may pass over into 

 tumors. 



Objections have been urged from various sides (Hansemann, 

 Hanau, Ziegler) to the opinions of Ribbert (who also accepts 

 inflammatory processes as possible causes for the inception of cel- 

 lular proliferations, as in case of epithelial cells). It has been 

 urged that if the above-mentioned displacements and isolations 

 of cells of epithelium were sufficient to call a cancer into exis- 

 tence, there necessarily should develop numberless cancers as 

 results of chronic inflammatory phlegmons ; that the cells of the 

 tumors ought not to appear merely as normal elements in luxuri- 

 ant multiplication, but the general rule should be that there exist 

 a special change, a differentiation of the cells (even though the 

 causes of cellular dift'erentiation be entirely unknown). 



Although we still await the solution of questions regarding 

 the conditions which underlie the origin of tumors, and concerning 

 the transformation of this or that kind of cell into tumor cells, 

 it is at least certain that tumor cells are tissue elements zvhich 

 hare become independent and m(iy be looked upon as cells zvhich 

 have actually become parasitic. This conception of the nature of 

 tumors (for which from this point of view the name autoblasto- 

 mata, proposed by Klebs, is most appropriate) has received im- 

 portant support in the extremely interesting experimental studies 

 of a veterinarian, C. O. Jensen. This investigator succeeded in 

 carrying a carcinomatous tumor of a mouse through nineteen 

 generations in mice by transplantation, and in demonstrating that 

 infection played no part in the process but that the transplanted 

 tumor cells, themselves parasitic upon the individuals in whom 



