THE BRADSHAW LECTURE 13 



in three of his private patients, and one in five or 

 six among hospital patients; whilst Harrison 

 Cripps, thirty-three years ago, showed that if the 

 evidence of heredity derived from collaterals and 

 doubtful cases were excluded, there remained 

 only a number similar to that expressing the 

 normal frequency of cancer to the whole popula- 

 tion. Dr. Bashford states that among persons 

 over the age of thirty- five the chance that a 

 man will die of cancer is one in eleven, and of 

 a woman above the same age one in eight ; 

 and so great is the frequency of cancer as a 

 cause of death above that age, that in one of 

 every two families a parent or a grandparent 

 will, on an average, have died of cancer. The 

 influence of heredity in man must therefore be 

 regarded as insignificant. It is true that by 

 careful selection and in-breeding Dr. Bashford 

 has produced a race of mice more liable to 

 spontaneous cancer than those of a sound stock, 

 but he warns us that experiment shows that 

 those of cancerous stock are not more liable to 

 implanted cancer than others. 



To my mind we arrived half-way to the dis- 

 covery of the cause of cancer when it was shown 

 that the disease was inoculable in animals of the 

 same species. We are dealing with a mildly con- 



