TUMORS 153 



is immune to this growth. This occurs in mice, where 

 tumors are transferred from one mouse to another, and 

 it has been established that recovery also occurs, though 

 rarely, in human beings. 



Ascitic fluid from an individual who had recovered 

 from cancer has been found to retard the growth and 

 cause the disappearance of cancer in another individual 

 into whom it was injected. Thus, while the cause of 

 cancer remains a mystery, the conquest of the age-old 

 scourge seems about to be realized. 



Cancer occurs in all parts of the body where epithelial 

 tissue exists. Among the more frequent seats of the 

 growth may be named the skin, stomach, intestines, 

 esophagus, tongue, rectum, mammary gland, ovaries, 

 liver, kidney, prostate, and testicle. 



Histologic Characteristics of Cancer. In sarcoma the 

 epithelial cells are distributed fairly uniformly through 

 the stroma, each cell being surrounded by connective- 

 tissue fibrillae, the connective tissue preponderating. In 

 carcinomata the epithelial cells preponderate and are 

 gathered in groups or cell-nests, which are surrounded by 

 a stroma of connective tissue. This alveolar structure is 

 always characteristic of carcinoma, no stroma penetrat- 

 ing between the individual cells, as in sarcoma. These 

 epithelial plugs infiltrate the surrounding tissue, invade 

 the lymph-channels, and are soon found in the regional 

 lymph-glands. From the glands the general circula- 

 tion is invaded and metastatic tumors occur in distant 



