108 SCIENCE PROGRESS 



every species of animal subject to cancer, there is also a 

 different parasite for each of the many different kinds of 

 malignant growths. The different kinds of malignant growths 

 found in man are found also in other animals. For instance, 

 cancer of a gland is similar and has similar varieties in mice 

 and men, both microscopically and in general behaviour. It 

 would therefore be necessary to assume that the widely diver- 

 gent varieties of the cancer parasite in man have representa- 

 tives in the independent groups of parasites belonging to each 

 variety of animal. 



Cancer of the uterus may arise during pregnancy but the 

 disease is not transferred to the offspring ; vice versa, a child 

 may be born with malignant disease but the mother will be 

 free from it. This does not appear to be compatible with a 

 parasite which has such free powers of migration as a parasite 

 causing malignant growths must necessarily possess. 



There are some parasites known to cause specific diseases, 

 which may also be among the causes of cancer. The parasite 

 of syphilis is an example. But to say this is not to suggest 

 that the parasite of syphilis or any other parasite is the cause 

 of cancer. That diseases and conditions producing chronic irri- 

 tation and inflammation and consequently an unusual multipli- 

 cation of the cells of a particular area should cause some of the 

 cells to pass out of somatic co-ordination and thus originate 

 a malignant growth, seems to be in every way in accordance 

 with what we know of cancer. A specific parasite is in no way 

 required in framing an adequate explanation and the difficulties 

 in the way of conceiving a micro-organism to be possessed of 

 the necessary qualities appear to be insuperable. The theory 

 of somatic co-ordination or cell autonomy, as set forth in the 

 last number of Science Progress, though affording a poorer 

 prospect of a speedy discovery of a cure, is compatible with all 

 the known facts. The conception of a parasite has been carried so 

 far, however, that a process has been described by which certain 

 bacteria multiply either in the body of the host or in artificial 

 cultures in such a way that exact representations are produced 

 of the minute structure of the individual cells and of the 

 arrangement of the groups of cells found in different kinds of 

 tissue. 1 The author of the account certainly does not say 



1 Marie Bra, Culture in Vitro des Cellules Canc<freases (Paris : A. Poinat, 

 ii, Rue Dupuytren, 1909). 



