DIMORPHISM AND POLYMORPHISM 37 I 



this disease only appears in men, the pathological variation 

 must affect the ' male ' half of the determinants for the cells of 

 the blood-vessels of the person affected, and we may compare 

 it with the variation which occurs in the cells constituting 

 the larynx, the determinants of which must certainly be re- 

 garded as being double, and as undergoing variation in the 

 • male ' half. The decision as to which halves of the double- 

 determinants in the idioplasm are to be active during embryogeny 

 and which passive, takes place simultaneously with that as to the 

 sex of the embryo, as is proved by the case of hermaphrodite 

 bees. It is therefore self-evident that this disease must remain 

 latent — i.e.. no diseased formation of the tissues whatever can 

 be produced — in the case of every female descendant of a 

 ' bleeder,' for in them the • female ' untransformed halves of the 

 determinants for the cells of the blood-vessels become active. 

 If, however, the offspring develops into a male, the pathologi- 

 cally transformed • male ' halves of these determinants become 

 active, and the disease can develop, provided that a stronger 

 hereditary influence is not exerted in the formation of the blood- 

 vessels of the healthy maternal side, so that the tendency to 

 disease, which has been derived from the father, is overcome by 

 the healthy tendency inherited from the mother. This was the 

 case in four generations of a family of ' bleeders,' observed 

 by Chelius, Mutzenbecher, and Lossen, — * the sons were not 

 affected. In another case described by Thulasius-Grandidier, on 

 the other hand, the disease was transmitted from the father to the 

 male members of three generations. We can understand both 

 cases from our point of view, for in no instance is an individual 

 variation due to the variation of the corresponding determinants 

 in all the ids of the germ-plasm, but only in the majority of them. 

 But this majority may become reduced to a minority at every 

 ' reducing division ' and every time amphimixis occurs, the varia- 

 tion thus ceasing to manifest itself. As soon therefore as only 

 a small majority of the ids contain '■ haemorrhagic determinants,' 

 a considerable number and hereditary force of the healthy 

 maternal determinants for the blood-vessels would preponderate 

 over the morbid paternal ones, and consequently the male 

 descendants would not inherit the disease. If, however, a con- 

 siderable majority of • haemorrhagic determinants ' were present 



* Klebs, ' Lehrbuch tier pathologichen Anatomic.' 



