CHROMOSOMES IN MAN 301 



families, and it is therefore likely that every one has some chro- 

 mosomes with a predisposition to some disease, such as phthisis, 

 or gout, or diabetes, or " nerves." A mosaic made up of con- 

 tributions from eight famihes can hardly avoid some such taint. 

 But the important point. Prof. Ziegler continues, is this,— what 

 numerical proportion do the tainted chromosomes bear to the 

 untainted ? If 3 out of the 24 have a diabetic taint, this will 

 mean much less than if there were 12 tainted. It follows that 

 taint on both sides of the house is particularly dangerous. 

 Ziegler gives the following illustrative schema. 



Father — with marked taint, inherited from his father 

 and mother, as shown by the dark chromo- 

 somes — 13 out of 24. 



000 ••• ••• ••O 00« ••• %Q0 000 



Three mature sperm -cells I ' vj vj 



showing three different \b.000 ••• #00 000 

 combinations [,. 0«» 000 000 000 



Mother — normal, though with a latent taint, inherited 

 from her mother, as shown by the dark 

 chromosomes — 4 out of 24. 



000 000 000 000 0«* % % O 000 000 



Three mature egg-cells 



' d. o o % ••• 000 000 



showing three different \e.Q^% OOO 000 OOO 

 combinations '/OOO 000 OOO OOO 



It is evident that the child resulting from a x d would have 

 a badly tainted inheritance, that another resulting from ex/ 

 would have a good inheritance, and that another from c x e 

 would be in the same position as the mother, and so on. 



§ II. Practical Considerations 



Pessimism unwarranted. — A consideration of the extent to 

 which predispositions to disease form part and parcel of our 



