37^ the germ-plasm 



2. Pathological Dimorphism: Hemophilia. 



In connection with the attempt to trace sexual dimorphism 

 to its origin in the idioplasm, I will now make a few remarks 

 with regard to a certain disease — or rather structural anomaly 

 — which affects the human race, and which. I believe, will be 

 better understood from this point of view ; the analysis of it 

 may, moreover, possibly throw a new light upon the causes 

 of sexual dimorphism. 



This anomaly is known as hcemophilia^ and although of rare 

 occurrence, it has been very accurately observed in a number of 

 cases, and is known to be transmitted in a marked degree and 

 in a very peculiar manner. It only occurs in the male members 

 of a family, but is transmitted by the female members, and in 

 this respect resetnbles a secondary sexual character. 



The disease, however, is apparently not connected with the 

 sexual organs, or with those parts which differ in the two 

 sexes. It consists in an abnormal flaccidity of the walls of the 

 blood-vessels, in consequence of which slight injuries cause 

 serious haemorhage, which cannot be easily stopped. As the 

 blood-vessels are developed from certain cells of the so-called 

 mesoblast or * parablast,' haemophilia is described in many 

 text-books on pathological anatomy as an anomaly of the 

 ' parablast ' or ' Bindegewebekeim.' It must certainly be assumed 

 that this disastrous variation in the blood-vessels — or rather of 

 the cells from which the blood-vessels are formed — is due to 

 some variation in certain mesoblast cells which cannot be more 

 definitely defined at present. The determinants for the cells of 

 the blood-vessels must in this case have varied in some way or 

 other in the germ-plasm of the individuals affected, and the anom- 

 aly must orighially have occurred in a male individual. There 

 is apparently no reason why a similar variation of the deter- 

 minants should not take place in a female, and cases of women 

 exhibiting the haemorrhagic diathesis may perhaps still be ascer- 

 tained. The exclusive transmission of this anomalous condition 

 to the male sex seems to me, however, to indicate that the deter- 

 minants for the blood-vessels differ in men and women, in spite 

 of the apparent similarity of the vessels themselves: — these 

 determinants must be double. 



On this assumption, we can easily account for the otherwise 

 mysterious phenomena of heredity observed in these cases. As 



