1912.] TO THE TUMOR PROBLEM. 203 



The growth consists of spindle-shaped cells supported by a 

 scanty, vascular framework ; and the sole differentiation which these 

 cells undergo is to an attenuated form with the production of a few 

 intercellular fibrils. In the disposition of the cell-strands and bundles 

 there is no suggestion of focal arrangement such as frequently in- 

 dicates, in the case of the granulomata, the presence and position 

 of an exciting cause ; while at the growth's borders a cellular reac- 

 tion is practically absent. The tumor elements multiply rapidly by 

 mitosis and amitosis, and the neoplasm grows, not only by expan- 

 sive enlargement but also through an active invasion and replace- 

 ment of the normal structures by tumor cells. In the course of 

 the invasion tumor cells frequently penetrate the walls of blood or 

 lymph-vessels, and are freed in the circulation. By their transpor- 

 tation, lodgment and growth secondary sarcomata are caused at 

 points distant from the primary mass. This important characteristic 

 of tumors in general has been placed beyond doubt as regards the 

 avian growth by means of direct experimentation. The host, which 

 at first seems unaffected by the tumor, emaciates as the growth in- 

 creases in size, and, if it escapes intercurrent processes eventually 

 dies in coma. 



The conditions which determine the success or failure of the 

 sarcoma when transplanted to a new individual are in general refer- 

 able, as are those of its behavior and dissemination, to the sarcoma 

 cells as such. The influence of variety of the host and of blood-rela- 

 tionship has already been referred to. Young hosts prove most 

 favorable, as for all transplantable tissues, normal or neoplastic. 

 Hosts which are ill of causes that involve emaciation are relatively 

 unfavorable, a circumstance noted in its relation to mammalian 

 growths by other workers, and especially interesting because these 

 hosts are more susceptible, as a rule, to the frankly infectious 

 processes. A certain proportion of hosts, although of the proper 

 variety for the tumor's growth, manifest a resistance such that it 

 does not develop when implanted in them ; while others in which 

 the growth has developed and retrogressed are completely resistant, 

 for a time at least. Similar types of resistance have already been 

 demonstrated for the tumors of rats and mice. Furthermore they 



