mi OBGAK8 "i mi. M1DDL1 GERM-l I 



or even hours. The di-charire take* plan- by tin- rupture of t he 



oonnective tissue envelope, which cause* tin- eggs t> escape into the 



body-cavity, as in the FM.e>and most of the Amphibia. After the 

 elimination, the OVary, which up to thi- linn- was extraordinarily 

 large and took up mo.M of tin- space in the tx>d\ ca\ ity. >hrivi-U into 

 a very small cord and now encksefl only tlie young germs of ova, 

 part of which arc defined to inatun- during tli- in-\i year, 



Tlic formation of the follicle take> place in a somewhat ditlen-m 

 Way in Maininals. The follicle originally contain-. a> in the n-inainini: 

 Vertebrates, only a single c^ and a >in.^le layer of follicular ci-ll>. 

 which are at tirM llat. then cul.ical. then cylindrical (fig. 216 /). 

 For a loni: time these cells envelop the egg as a single layer, but 



Fig. 217 A and B. -Two stages :n the development of the Graafian follicle. A with the follicular 

 fluid beginning to be fonm-l ; l> ^ ith a greater accumulation of it. 



, ; fz, follicular cells ; fz\ follicular cells which envelop the ovum and constitute the 

 discus proligerus; /; follicular fluid (liquor folliculi) ; fk, follicular caiwule (tht-ca 

 folliculi); :p. zora 



they then rrow. undergo division, and are converted into a thick 

 envelope of many layers. But the difference from the course of 

 development described above becomes still greater, owing to the fact 

 that a fluid, the liquor folliculi, is secreted by the proliferated 



follicular cell>, and collects in a small cavitv at the side of th 



! -I/)- 



In consequence of a considerable increase of the fluid, the originally 

 solid follicle becomes converted finally into a large or small ve.-icl<- 

 (fig. 217 /?), which was discovered inorr than two hundred years ago 

 1'v the Hollander REGXIER DE GRAAF and was held to be the 

 human ovum. The structure has al>> l>ecn named after mm the 

 11 a n fal/iclf. Such a follicle (fig. 217 B) now c..n>i>i> of (1) an 

 outer connective-tissue, vascular envelope (/k), the theca folliculi; 



