XII] Recessives in Man 225 



in the case of another sex-Hmited disease — a peculiar 

 paralysis of a "peroneal" type, studied by Herringham*. 

 Some definite disturbing complication must be looked for 

 in these phenomena, and the statement that the factor is 

 dominant in males, and recessive in females, can only be 

 taken as giving a qualitative description of its behaviour. 



In Gowers' disease we have perhaps also to deal with 

 more than one condition, and the evidence suggests that 

 the recessiveness in females is not universal. 



Tabular representations of the most probable expecta- 

 tions in the case of a sex-limited condition are given in 

 Figs. 33 and 34. 



Recessive Variations in Man, 



As so many abnormalities are known to behave as domi- 

 nants with some consistency it is perhaps surprising that 

 we have no quite positive case of pathological conditions 

 behaving as recessives in man. The evidence regarding 

 the normal light eye-colour has already been given, but this 

 as yet stands practically alone. Hurst (162) has given 

 some further facts suggesting that the musical sense is a 

 recessive, but great and obvious difficulties make it very 

 hard to obtain convincing proofs in that case. 



In regard to diseases that may be recessive, there 

 are several records which are suggestive, but little that 

 amounts to proof. Naturally, as evidence of direct trans- 

 mission is not to be expected, the likeliest place to look 

 for recessives will be among those conditions which have 

 been noticed as coming with special frequency in families 

 resulting from consanguineous matings. In such matings, 

 and particularly in those of first cousins, bearers of similar 

 recessive characters may come together, and thus by the 

 meeting of two similar germs in fertilisation offspring 

 exhibiting the recessive character may be formed. The 

 comparatively frequent appearance of a variation among 

 the children of such unions is thus prima facie a suggestion 

 that it is a recessive to the normal. This has been observed 

 very noticeably in regard to retinitis pigmentosa, a degenera- 

 tive disease of the retina. In Herrlinger'sf collection of 



* Herringham, W. P., Brain, xi. 1889, p 230. 



t Herrlinger, "Ueb. d. Aetiologie d. Retinitis Pigmentosa," Jnaug, 

 Diss., Tiibingen, 1899. 



B. H. 15 



