APPENDIX A 269 



inherent endeavour, each of the other tissues, other than 

 the cartilage, furnishes a restraining substance, and co- 

 ordinates its growth with the rest." If this is true, and 

 few will nowadays be found to doubt that it represents, 

 at any rate partially, the actual machinery through which 

 ordered growth is obtained, it follows inevitably that the 

 want of a particular restraining body should result in the 

 disorderly growth of some tissue specially apt to pro- 

 liferate. Such are epithelium and connective tissue, the 

 agents of malignancy, and in view of the whole of the 

 phenomena of malignant disaster and repair it is perfectly 

 legitimate to infer that these two tissues are those which 

 react most powerfully upon each other. 



Other experiments by Shattock and Dudgeon are of 

 great interest and value, and at first sight may seem to 

 support the parasitic theory. Mice fed with mouse-cancer 

 appear to have developed, (i) a round-celled sarcoma, (2) 

 an invasive epithelioma of the mediastinal glands, (3) an 

 invasive endothelioma. Such results are, however, by 

 no means convincing. Abnormal results from highly 

 abnormal foods are what might be expected, on the general 

 theory of physiological balance. Salmon and trout fry 

 fed upon pig's liver develop a thyroidal overgrowth which 

 later may become malignant, and the ingestion of foods, 

 carrying stimulating or inhibiting products or both, should 

 on the developmental view have abnormal results. It 

 has been said that excessive thyroidal medication is in 

 some cases followed by cancer. Moreover, the statement 

 by the two workers above mentioned really supports the 

 developmental view. They say " the first striking thing 

 is that the tumours of the three mice have not the same 

 histological character, and that none can be viewed as 

 having resulted from the growth of implanted cells." If, 



