Embryo. 



mm. 



2 to 4 



4 to 10 



10 to 15 



15 to 20 



20 to 25 



Chorion. 



cm. 



less than 1.5 

 1.5 to 3 

 2.5 to 4 

 3.5 to 5 

 4.0 to 6 



172 STUDIES ON PATHOLOGIC OVA. 



the weight, of the empty chorionic vesicle and that of the cyema would be more 

 reliable data for a determination of a correlation between the two. 



Very few data on this matter are available to us in the literature and we must 

 bear in mind that it is not yet possible to distinguish between the early normal and 

 the abnormal. Whether or not the relationship between the dimensions of the 

 cyema and the chorionic vesicle can be used, as suggested by Giacomini (1894), 

 for distinguishing between the normal and abnormal, it is impossible to say at 

 present. But even if such a criterion can not be obtained, a comparison between 

 the size of the cyema and the chorionic vesicle nevertheless 

 may reveal fluctuations in the one or the other, or in both, 

 which might otherwise be overlooked. 



Without reference to the excellent older observations 

 of Velpeau (1855), His (1882) concluded that chorionic was 

 related to amniotic size in early specimens, as shown in the 

 accompanying table. 



Giacomini stated that embryos with a length of 2 to 4 mm. are contained in 

 vesicles 1.5 cm. long; embryos 4 to 10 mm., in vesicles 1.5 to 3 cm.; embryos 10 

 to 18 mm., in vesicles 2.5 to 4 cm.; embryos 15 to 20 mm., in vesicles 3.5 to 5 

 cm. ; and embryos 18 to 20 mm., in vesicles 4 to 6 cm. long. Giacomini also stated, 

 as did His (1882), that the amnions of embryos less than 10 mm. long invest the 

 latter closely and His further stated that the amnion is 1 to 3 mm. distant from 

 embryos 11 to 15 mm. long and that it had fused with the chorion when the embryo 

 had gained a length of 2.5 cm. Schaeffer (1898) stated that embryos 1.15 mm. 

 long are contained in vesicles of 2.5 to 2.7 cm.; embryos 3 mm. long in vesicles of 

 2.5 cm.; and embryos 8 mm. long in vesicles 7.5 to 8.5 cm. J. Kollmann (1898) 

 gave the relation of chorionic to embryonic size the same as His. Since His and 

 Kollmann give only one chorionic measurement, it is impossible to surmise what 

 their conception of the form of the chorionic vesicle was, but His's table suggests 

 that the relation between embryonic and chorionic length varies from 1-5 to 1-2 

 by the time the embryo has reached a length of 2 cm. 



Eternod (1909 a ) emphasized the fact that the conceptuses described by 

 Reichert, Ahlfeld, and by himself, all were lenticular in form and also flattened 

 somewhat upon one of their faces. The same thing is true of those reported by 

 Bryce and Teacher, Peters, von Spee, and also of some other specimens. Eternod 

 stated that while early conceptuses are lenticular, they later become ovoid, and 

 still later more spherical. According to Eternod, the portion toward the basalis 

 is flattened the most, while that toward the capsularis is more curved. 



Since some of the conceptuses called lenticular by Eternod are so very small, 

 their shape scarcely can be attributed to the influence of the surrounding mus- 

 culature. Hence it would seem that the human conceptus soon loses the inherent 

 sphericity undoubtedly possessed by the ovum. If, as Eternod thought, the villi 

 of early conceptuses are zonal or annular, with two free surfaces which he desig- 

 nated as dorsal and ventral, a further source of variation in the measurements of 

 young specimens would be introduced. 



