272 HEREDITY AND DISEASE 



§ 6. Particular Cases 



Colour-blindness. — Horner, cited by Klebs, gives an inter- 

 esting family history, showing the hereditary persistence of 

 Daltonism or colour-blindness. The black letters indicate 

 the affected subjects : 



HI 



\ 



I I 



F F 



I I 



M M 



I I 



I I I 



F F F 



M M 



M M 



I I I 



F F F 



I I 1 



MM M F M M F F M MM V F M F F F F 



The following pedigree of a family containing colour-blind 

 members was worked out by Dr. Rivers, among the Todas, an 

 Indian hiU tribe. It illustrates the " Knight's move " descent, 

 as it may be called. The colour-blindness is exhibited in male 

 members of the pedigree, but the females, though unaffected 

 themselves, may transmit it to their male offspring. 



I I 



M / 



m M / / M /" / m M 



I I I I ' I 



III II Ml I I I I I II I I I I I 



m m f t f yi f f M / M / / ;;? M tn m m m f 



\ I 



VI 111 



Short-sightedness. — It is generally admitted that short- 

 sightedness is due to an inborn peculiarity in the structure of 

 the eye, occurring in various degrees. In itself it can hardly 



