HEREDITY OF DISEASES. S3 



rather than the exception, in the transmission of con- 

 stitutional peculiarities. 



In speaking of the heredity of cancer, Dr. Paget 

 says : " Let it be observed, this tendency to cancerous 

 disease is most commonly derived from a parent who 

 is not yet manifestly cancerous ; for, most commonly, 

 the children are born before cancer is evident in the 

 parent; so that, as we may say, that which is still 

 future to the parent is transmitted potentially to the 

 offspring. Nay, more, the tendency which exists in 

 the parent may never become in him or her effective, 

 although it may become effective in the offspring; 

 for there are cases in which a grandparent has been 

 cancerous, and, although his or her children have not 

 been so, the grandchildren have been. Let me repeat, 

 the cases of hereditary cancer only illustrate the com- 

 mon rule of the transmission of hereditary properties, 

 whether natural or morbid. Just as the parent, in 

 the perfection of maturity, transmits to the offspring 

 those conditions, in germ and rudimental substance, 

 which shall be changed into the exact imitation of the 

 parent's self, not only in the fullness of health, but in 

 all the infirmities of yet future age ; so, also, even in 

 seeming health, the same parent may communicate to 

 the materials of the offspring the rudiments of yet 

 future diseases ; and these rudiments must, in the case 

 before us, be such modifications of natural composi- 

 tions as, in the course of many years, shall be devel- 

 oped or degenerate into materials that will manifest 

 themselves in the production of cancer." 1 



In the cases of hereditary disease already noticed, 



1 " Surgical Pathology," p. 639. 



