290 C. G. CAMPBELL 



ical pattern with such inherited tendencies, we may cite a case reported of 

 identical twins who were born of a tubercular mother in Wyoming. The 

 mother survived their birth only a very short time and they were at once 

 separated and were never again together. One twin was reared in Wyoming 

 and the other in Arizona. At about the age of eighteen, and within six 

 months of one another, they both developed incipient tuberculosis. This 

 is further remarkable, as the development of incipient tuberculosis is of 

 exceedingly rare occurrence in the climate of the Mountain States. Another 

 case has been reported of identical twins who both developed dementia 

 precox at approximately the same age. It is scarcely to be denied that such 

 cases go strongly to show the inheritance of pathological physical patterns 

 which are practically identical. Such observations lead us to suspect that 

 hereditary predispositions to disease may prove to be far more precise and 

 inevitable in their action than we have hitherto been inclined to think. 

 There is already sufficient positive evidence to warrant the inference that a 

 hereditary factor enters in a greater or less degree into most disease. Many 

 competent observers have reached such a conclusion. Dr. Charles Mayo 

 has expressed the opinion, which we may be certain is not an immature one, 

 that a hereditary factor may be traceable in at least 60 per cent of disease. 

 Dr. William Carpenter MacCarty has designated two basic causative 

 factors in cancer, namely hereditary susceptibility on the one hand, and 

 prolonged irritation in a susceptible individual on the other. The greater 

 the hereditary susceptibility in individuals, the greater will be the incidence 

 of cancer. Experiments with mice have demonstrated that it is possible to 

 breed a race of mice that is readily susceptible to cancer inoculation, and 

 another race of the same strain that is wholly immune to such inoculation. 

 Now what in our present knowledge offers the greatest promise for the pre- 

 vention of cancer? Dr. MacCarty expresses the opinion that it lies in the 

 intermarriage of individuals without cancer heredity. We cannot afford 

 to neglect such an authoritative opinion, especially when it is realized 

 that the incidence of cancer has practically doubled in a generation. 

 Frederick L. Hoffman, in a careful analysis of the cancer record, shows that 

 the death rate from cancer in fifty American cities increased from 71.6 per 

 hundred thousand in 1906 to 122.3 in 1930. Some mitigation of this in- 

 crease might be found in the prolongation of the average life and the survival 

 of more people to what is called the "cancer age." But this can scarcely 

 lull us into the belief that a serious and dangerous increase in the most 

 terrible of diseases has not taken place. One cannot disagree with Dr. 

 Hoffman's conclusion that "the menace of cancer is at the present time a 

 more serious problem than ever before during the recorded history of the 

 disease." 



