HeTrman: Heredity and Disease 



79 



Why is it that so httle attention has 

 been given to heredity as a possible 

 factor in the causation of disease' In 

 the majority of cases the connection 

 is not so striking as to be immediately 

 apparent. Our family histories and pedi- 

 grees are very inaccurate and incom- 

 plete. Many physicians content them- 

 selves with an inquiry as to the health 

 of the parents and the brothers and 

 sisters of the patient. The facts are 

 not on the surface ; they have to be dug 

 out. If the unit character is recessive, 

 it may show itself in only a very small 

 number of the entire famil}^ in several 

 generations, and this character may 

 not always show itself in exactly the 

 same form. It is often extremely diffi- 

 cult to get a complete family history, 

 first, on account of lack of knowledge on 

 the part of the parents. Very few in- 

 dividuals can give a complete account 

 of the members of both branches of the 

 family. For this reason, several mem- 

 bers of the family should be interviewed. 

 Secondly, there is often a desire to con- 

 ceal unfavorable qualities or tendencies, 

 such, for example, as insanity or mental 

 defectiveness, and only with the greatest 

 tact can such information be obtained. 

 Compare, in Fig. 17, an original and a 

 revised pedigree as given by Goddard. 

 Thirdly, the children who present the 





■■ton •g 



D OMale.Female Normal 

 ■ • .. „ AfKcted 



H OMalcFen 



D 02.. a ., 



ale part Atfected 



Original pedigree 



©^ 



"Tl 



PEDIGREES OF POLYDACTYLISMi 



Tliat polydactylism is an inherited unit 

 character might be attested by the first 

 pedigree above, but the second chart, con- 

 taining only three isolated cases, shows the 

 greatest difference. There is undoubtedly 

 a great need for additional statistics to 

 establish its status definitely. (Fig. 18.) 



anomaly are frequently among the mis- 

 carriages, stillbirths, or those dying in 

 early infancy, and such cases may be 

 easily overlooked. For example, an 

 amaurotic family idiot may appear 

 nonnal during the first five months, 

 so that if such an infant died before 

 that time, the presence of the disease 

 would not be suspected. As has been 

 stated, if the unit character is recessive, 

 it may be noted in only a few individuals 

 in several generations; however, even 

 in the case of a unit character, which is 

 usually considered as dominant, a great 

 variation in the number of individuals 

 affected may occur. Fig. 18 presents 

 the pedigrees of two families in which 

 polydactylism occurred. The first is 

 that reported by Smith and Norwell 

 (Brit. Med. Jour., 1894, Vol. ii, p. 8), 

 the second by Struthers (Edinburgh 

 New Phil. Jour., 1863, Vol. xviii, p. 83). 

 This is an anomaly which would hardly 

 be likely to escape notice, even in a 

 child that died in early infancy; there 

 would be no reason for concealing the 

 facts, and still the two charts show the 

 greatest difference in the number of 

 individuals affected. 



1 The first is that reported by vSmith and Norwell (British Medical Journal, 1894, Vol. ii, p. 8), 

 the second by Struthers {Edinburgh New Philadelphia Journal, 1863, Vol. xxviii, p. 83). 



R e V i sed pedigree 



-<g~^ 



\E\ ®Male,Fein9le Normal S I^Male. Female prob.Norma l 

 BO., .. Affected |3 © „ „ ,, Affected 



MONGOLIAN IMBECILITY 



Two charts by Goddard are shown above, 

 the first the original and the second the 

 revised form, which was drafted when 

 additional information could be secured. 

 It may immediately be seen that erroneous 

 conclusions might be based on the original 

 chart. (Fig. 17.) 



