THE INHERITANCE OF DISEASE 513 



out that the pigment when present is carried by a special 

 type of cell with no other known function than that of 

 producing and locahzing the coloring matter. The pigment 

 is produced by the oxidation (presumably by the associated 

 activities of particular ferments) of a particular colorless 

 substance. The final color depends on the amount of pigment 

 and the distribution of the cells which carry it. There are 

 evidently various points at which the controlhng factors 

 which genetic theory postulates as multiple unit characters 

 could be operative. Complete absence or reduction in 

 number of the chromophore cells, variations in their general 

 functional activity, or differences in any of the particular 

 chemical (fermentative) activities underlying the pro- 

 duction and "ripening" of the characteristic pigment are 

 obvious and distinct loci where controlhng factors might well 

 exert their force. One of the tasks for the future is to analyse 

 and locate these factors in precise terms with reference 

 to general and particular structures and functions. 



Other chapters have given consideration to the more 

 general aspects of inheritance and its social significance. 

 This one may well be concluded by explicit reiteration of 

 the rather obvious fact that any application of our knowledge 

 of the inheritance of disease to the broad purposes of race 

 betterment must be through the development of ability 

 to control particular and individual cases. Our general 

 culture, our freedom from certain infectious diseases may 

 alike be immediately and largely a matter of social inheri- 

 tance. Our liability to those diseases, defects, and dis- 

 comforts which are controlled by the physical inheritance 

 must always be based directly on the qualities of the germ 

 plasm transmitted from father and mother to their children 

 and so to their grandchildren. 



We can perhaps sterilize certain obvious defectives and so 

 minimize the economic burden imposed by the maintenance 

 of institutions for their care. But we cannot so durably solve 

 the problems imposed by the fact that disabling defects, 

 diseases and tendencies to the development of disease are 

 inherited. The faulty germ plasm considering the multitude 

 of distorted conditions is too widespread for this. The 

 ancients when they wished to completely subjugate a 

 conquered enemy people "decimated" the population. 



