THEORIES AND PROBLEMS OF CANCER 



PART II 



By CHARLES WALKER, D.Sc, M.R.C.S., L.R.C.P. 



Director of Research Department, Royal Glasgow Cancer Hospital 



In order that the nature of the investigations dealt with in 

 these articles may be clear to the general reader, it is necessary 

 to say something about the character and varieties of malignant 

 growths. As was pointed out in the previous article, the cells 

 produced by the division of the ovum and subsequent genera- 

 tions of cells become arranged into two layers known as 

 epiblast and hypoblast ; groups of cells produced afterwards, 

 situated between these two layers, are known as the mesoblastic 

 layer. Different kinds of tissue are produced from these three 

 layers of cells. The skin is formed from epiblastic cells, the 

 lining of the alimentary canal from hypoblastic, the muscles 

 and bones from mesoblastic cells. Malignant growths may 

 occur in tissues composed of any of these three classes of cells ; 

 they are divided, however, into two great groups, carcinomata, 

 which arise in epiblastic or hypoblastic cells and sarcomata, 

 which arise in mesoblastic cells. Carcinoma includes epithe- 

 lioma, which is probably what was originally known as cancer. 

 It is practically question that all carcinomata are of the same 

 nature. Carcinoma is essentially a disease of middle and old 

 age; sarcoma occurs chiefly in young individuals and children 

 may be born with it in an advanced stage. Authorities who 

 have studied the matter and are competent to judge are now 

 agreed that the phenomena involved in both carcinomata and 

 sarcomata are essentially similar in character and that like 

 problems have to be faced in either case. It seems probable 

 that the real difference is that one class of tissue is more subject 

 to certain changes at one period of life, the other class at 

 another period. 



Abnormal growths of tissue — collections of cells— may be 

 roughly divided into two classes, benign and malignant. In text 

 books it is stated that one of the essential differences between 



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