248 ON VARIABILITY AND ADAPTATION 



believe that my original hypothesis is sound. I would conclude 

 by recalling this to you. There are many examples that I might 

 take as illustrative, but perhaps the best is that worked out by 

 my late colleague, Dr. Wolbach, 1 now assistant professor at 

 Harvard — his study of the mode of origin of that modern disease, 

 X-ray carcinoma. He had at his disposal material from a long 

 series of X-ray burns, and so was able to follow well all the 

 stages. 



Paradoxically, the X-rays have singularly little effect upon 

 the epidermis and epidermal cells, but they influence profoundly 

 the underlying corium. There in the earliest stage there are 

 set up marked lesions, telling especially upon the vessels and 

 lymph spaces — proliferation and desquamation of the endothelial 

 cells, thromboses, and other evidence of severe vascular dis- 

 turbance ; and it is secondary to this that the epiderm is affected 

 and tends to ulcerate. Those changes, to be brief, lead to a 

 form of inflammatory fibrosis of the subepidermal tissue, and 

 as a result the nutrition of the epiderm is gravely reduced. In 

 some places the reduction is so great that the cells necrose, and 

 ulceration is the result. In other places the effects are not 

 so intense, and one gets what I would term the " poor curate " 

 phenomenon. You will have observed that the well-fed million- 

 aire and his wife are apt to be childless, whereas the curate and 

 his wife have a family in inverse size to their capacity to support 

 them. That appears to be a law of nature : there is a certain 

 nutritive minimum at which, it would seem, the preservation of 

 the species becomes of greater consequence than that of the 

 individual, and multiplication ensues, to the detriment of the 

 individual, but on the off-chance that a few out of the abundant 

 progeny may survive. And so it is that in these cases where 

 the epiderm is not wholly necrosed, its cells multiply ; and now 

 is observed a phenomenon apparently of the same order as that 

 first observed by Bernhard Fischer after inoculating a mixture 

 of olive oil and Sudan iii. into the tissues of the rabbit's ear 

 (an observation abundantly confirmed), namely, the growth 

 downward of the epithelial cells toward the oil. In these X-ray 

 burns the actively proliferating epithelial cells grow downward 

 through the dense fibrosed cutis toward the nearest source of 

 nutrition — the underlying vessels. 



1 Wolbaoh, Journ. of Med. Research, xii., 1909, 415, 



