SOME CATALYTIC ASPECTS OF DISEASE AND DRUGS 227 



The following are mentioned by Snyder as among the many 

 diseases transmitted by heredity: 



Eye and Ear: albinism (the eyes are pink, since lack of pigments 

 permits the blood color to come through); color blindness; deaf- 

 mutism. 



Skin: icthyosis; absence of sweat glands; beaded hair (which 

 breaks off, leaving bristle-like pieces); Von Recklinghausen's dis- 

 ease (due to a dominant gene), a neurofibromatosis affecting skin 

 and nerves; Mongolian spot. 



Skeleton and Muscles: polydactyly (extra digits); syndactyly 

 (digits joined or "webbed"); "crab-claw" and like imperfections; 

 club-foot; myotonia congenita (Thomsen's disease); myopathy 

 (progressive muscular dystrophy). 



Blood: hemophilia; anemia; troubles due to blood groups, in- 

 cluding Rh factor. 



Nerves: a variety of nervous conditions, including insanities 

 and Huntington's chorea. The violent involuntary movements 

 in this disease generally appear only in adult life, and follow de- 

 generative changes of ganglion cells of the frontal cortex and of 

 the cordate nucleus and putamen. 



C. B. Davenport states 24 that traits known to have a chemical 

 basis have the cleanest-cut genetics, e.g., blood groups, cretinism 

 (thyroid deficiency), amurotic family idiocy (a recessive associated 

 with the storage of phosphatides). "The relation between the 

 somatic expression of a trait and its chemical basis may be remote. 

 Thus hardness of hearing seems to depend on a defect in calcium 

 metabolism such as causes abnormal bone formation in the oval 

 window of the inner ear and simultaneously in other parts of the 

 temporal bone. In the latter case there is reason for concluding 

 that the result depends on a dominant factor in an autosome 

 which modifies the reaction of the mesenchyme and a sex-linked 

 gene which perhaps affects calcium metabolism. Indeed it seems 

 probable that in time chemical errors in the body may throw light 

 upon the chemical processes of development." 



A rather rare kind of recessively heritable metabolic error is 

 alkaptonuria, first described by von Boedecker, 24a and recently ob- 

 served in an American Negro family. 25 In these cases the urine 

 contains homogentisic acid, shown by M. Wolkow and E. Bau- 

 mann 26 to be 2,5-dihydroxyphenyl acetic acid, which is labile and 

 oxidizes, turning the urine black. Apart from occasional blacken- 

 ing of cartilage (ochronosis) no other symptom is evident. Homo- 



