THE PINEAL BODY 



73 



organ shows the first appearance of the epiphyseal complex at 

 the stage of 30 mm. embryo where it takes the form of a wide, 

 single evagination immediately cephalad to the posterior com- 

 missure. This evagination contains a recess in free communica- 

 tion with the third ventricle (fig. 40). 



In a cat embryo of 51 mm. a notable change has taken place 

 in the epiphyseal anlage shown in the fact that the original 

 single evagination has now become subdivided into two smaller 

 sacs separated by a marked thickening in the original diver- 

 ticulum. This is shown in figure 41. 



M 



Fig. 39 The pineal body in Cavia cobaya, according to d'Erchia, 1896. 

 Ds , dorsal sac; Ch., cornmissura habenularis; Sch., pars intercalaris; Ep., 

 epiphysis cerebri; M, midbrain. 



In so far as is known no similar occurrence has been noted in 

 mammals with the exception of a single report by Cutore 74 in 

 the new-born Bos iaurus in which two distinct evaginations in 

 the epiphyseal complex were observed. This appearance was 

 interpreted by Cutore as indicative of an anlage both for the 

 pineal and parapineal organs, and if such an interpretation 

 seems acceptable, it might be applied to the appearances just 

 mentioned in the embryos of the domestic cat. The tendency 

 for this double diverticulum to persist through the development 



