FACTORS IN THE RESISTANCE OF GUINEA PIGS 

 TO TUBERCULOSIS, WITH ESPECIAL 

 REGARD TO INBREEDING AND 

 HEREDITY 



DR. SEWALL WRIGHT, S.D., AND DR. PAUL A. LEWIS, M.D. 



WAsnixGTOx, D. C, AND The Henry Phipps Institute, The 

 University of Pennsylvania, Philadelphia, Pa. 



In the pre-bacteriologic era physicians were quite gen- 

 erally of the opinion that heredity played a large part in 

 resistance or susceptibility to tuberculosis. Following 

 Koch's demonstration of the part played by the BacUlus 

 tuberculosis in the etiology of the disease it was recog- 

 nized that the hereditary influences might be only ap- 

 parent ; the disease being established in any family there 

 was evidently an immeasurably increased chance of inter- 

 familial infection; and as a consequence of this uncer- 

 tainty of interpretation it has become quite customary- to 

 regard hereditary influences, properly considered, as a 

 negligible factor. 



Pearson^' 2 and Goring^ compared the correlation be- 

 tween parent and offspring, in incidence of the disease, 

 with that between husband and wife. The effects of un- 

 favorable conditions and the chances of infection might 

 be about as great in one ease as in the other, while 

 heredity would be a connnon factor only in the first case. 

 Pearson dealt with upper class families of which one 

 member was being treated in a certain sanitarium. The 

 correlation between parent and offspring came out about 

 .50, in the usual scale, in which 1.00 is perfect correla- 



1 Pearson, Karl, 1907, "A First Stu.ly of the S;t;itisti<'s of Puln.onarv 

 Tuberculosis." Dulau & Co., Lon.lon. i.>(i 



2 Pearson, Karl, 1912, " TuVkm-cuIum^. ll, , . .li-y Knvironnicnt. " 

 Dulau & Co., London. 46 pages. 



3 Goring, Charles, 1909, "On the rnhci irnii. r of tlu> DiMthosos of Phthisis 

 and Insanity." Dulau & Co., London. pages. 



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