Cancer. 399 



filtered extracts arc not followed by success. Ehrlich {Berlin. 

 Klin. Woehenschr., No. 28, 1905; Xo. 2, 1906) and Loeb {Univ. 

 of Penna. Med. Bull., July, 1905) have both recorded the occurrence 

 of sarcoma succeeding the original carcinomatous tumors after 

 some generations of transmissions. This would not necessarily 

 suggest the direct transformation of the cancer into sarcoma, as 

 much as that in the course of growth the proliferating epithelium 

 had induced such changes in the connective tissue portions of 

 the lumr)r as to cause them to acquire an analogous energy of 

 atypical proliferation, and that perhaps this latter tissue or, what 

 perhaps is more ])robable, immune bodies, reactively de- 

 veloping to the cancer, have caused the disappearance of the epi- 

 thelium itself. The known spontaneous disappearance of cancers 

 (cf. Gaylord and Clowes : Sitrgcry, Gynecology and Obstetrics, 

 June, 1906) speaks in favor of the existence of such cytolytic factors. 

 Gaylord's success in obtaining a serum from mice spontaneously 

 recovering from cancers, which on injection into mice having in 

 their bodies actively growing tumors of the same strain cawses 

 them to recover, speaks in the same line ; and the fact that an ex- 

 tract of a tumor (v. p. 339) injected into the body of the original 

 animal having other nodes of the same growth in its body, strongly 

 supports the same idea. Tentatively then it may be held that in case 

 of cancers at least the present tendency is not so much to accept the 

 existence of a specific parasitic cause for the growth as to believe 

 that once established as an independent focus of growth by some 

 such method as is suggested in Ribbert's isolation theory, the epi- 

 thelial cells become themselves, as it were, practically parasitic in 

 the organism of which they were once an integral part : that they 

 grow as parasites and act as parasites : and that the body reacts to 

 their presence as it does to other parasitic organisms, and endeav- 

 ors (sometimes successfully) to produce cytolytic or other protec- 

 tive reactions which will tend to destroy the cancer cells. This 

 view opens an attractive and wide field for application in many lines, 

 not merely therapeutic, and suggests reasons which may explain 

 the special prevalence or special failure of secondary growths in 

 different systems and organs of the body, as it may be supposed 

 that all parts are more or less open by the lymph or blood streams 

 to the reception of secondary tumor emboli.] 



All other contributions dealing with cancer parasites (cancer 

 bacilli, blastomycetes, etc.) recognized by microscopic methods have 

 originated from mistaken interpretations of the microscopic pic- 

 tures presented in various examples. 



