SOME POSSIBLE BEARINGS OF GENETICS ON PATHOLOGY L3 



I propose now to pass in review some characters in man known 

 to be inherited, choosing preferably those that come nearest to 

 the field of pathology, or belonging to it. I shall begin with 

 comparatively simple cases, about which there can be little doubt, 

 and pass to more and more difficult situations. I am taking the 

 risk of reaching an anticlimax, but nevertheless such a procedure 

 will, I hope, serve our purpose this evening if I can point out 

 where the evidence is satisfactory and where it is deficient. 



My first illustration of inheritance in man may be said to be 

 a physiological one, mainly because we do not know at present any 

 structural or chemical basis for the reaction. 



Color-blindness in man is clearly a case of sex-linked inherit- 



XX? 



X i 



XYd" 



^SSSSS * sSeSSS -<^^S 



Fig. 6. Inheritance of color blindness of man which is sex-linked (i.e., 

 the factor for color blindness is carried in the X-chromosome). This X- 

 chromosome is stippled in the figure while the X-chromosomes for normal 

 eyes are represented by black X's. The color-blind eye is also stippled, and 

 the normal eye (which distinguishes between red and green) is here repre- 

 sented by an eye half black and half cross-lined. The 1st generation off- 

 spring (Fi) are normal eyed. In the 2d generation offspring, half the sons 

 are color blind. 



