384 INTERNAL SECRETIONS 



in some cases rudimentary testicles. The uterus is as a rule 

 underdeveloped, being small and thin. According to Keller 

 and Tandler the underdevelopment of the organs originating 

 in the female from the Miillerian ducts is particularly marked 

 when, the rudimentary gonad resembles a testicle. In these 

 cases the ducts of Gartner (the remains of the Wolffian ducts) 

 are particularly well developed, giving the impression of vasa 

 deferentia. In some cases there was even a partial descent of 

 the testis-like gonads. Some kind of seminal vesicles can be 

 detected, and they are especially well developed if the other 

 genital organs are of a more male type. Thus we see that the 

 freemartin is a case of intersexuality, which might be designated 

 in the old terminology as a pseudo-hermaphrodite sho\\ing a 

 combination of characters of both sexes, those of the female 

 being as a rule more marked. 



Both twins in cattle are normal, when both are of the same 

 sex, whether it be male or female. When the twins are of 

 different sexes, the male one is always normal, whereas the 

 female one is normal only in very rare cases, according to 

 Keller and Tandler, only in six per cent. Now the question 

 arises whether there are any structural differences in the 

 mutual relations between the foetuses, which could explain 

 why the female twin is generally abnormal, but is nevertheless 

 normal in some cases. For this purpose they examined the 

 membrane relations and the circulation in twins of cattle. 

 Although there were generally two corpora lutea, there was 

 as a rule a fusion of the two chorions. There were also in 

 most cases connecting blood vessels between both foetuses {Fig. 130). 

 Besides this some cotyledons had vessels arising from both 

 foetuses. It seems, according to Lillie, that the connection 

 between the circulation of both twins is already established 

 at a very early stage ; he found a fusion of the two chorions at 

 a stage when the foetuses had a length of only 10 to 20 mm. 



A detailed anatomical examination of the foetuses supplied 

 evidence that in opposite-sexed twins the female foetus has 

 abnormal internal genital organs, when there is a fusion of 

 the two chorions and a well developed connection between 

 the blood vessels. On the other hand, the female foetus was 

 found to be normal when there was no connection with the blood 

 vessels of the male foetus. It is the same in other mammals with 

 normal twins of different sexes or of the same sex (Fig. 131). 



