THE OVA AND OVARY IN MAN AND OTHER MAMMALIA. 191 



memoir we find an interesting history of the views of earlier 

 observers on the origin of the ova and Graafian follicles. 

 Waldeyer refers to the work of Valentin^i who, in 1838, 

 first demonstrated the branched and tubular glandular 

 structure of the ovary, and he makes special mention of the 

 observations of Pfliiger,^ who first described the ova in 

 mammals as arising out of the epithelium lining tubular 

 glands in the ovary, and the formation of Graafian follicles 

 from such tubular structures. Formerly the ova and 

 follicles were considered to be derived from the cells of the 

 stroma of the ovary. The observations of Pfliiger led to the 

 publication of numerous works on the origin and develop- 

 ment of the ova, and the tubular formations were soon dis- 

 covered in the ovary of the human subject, first by Spiegel- 

 berg. In Waldeyer's observations, however, we have the 

 most recent addition to our knowledge of the development of 

 the ova and the formation of the Graafian follicles, and the 

 following quotations from his work will place before us, 

 briefly, the conclusions he has drawn from them : 

 In summing up, Waldeyer thus remarks : 

 " As the chief result of my investigations, it must be 

 stated that both the eg§ and the follicular epithelial cells are 

 derived directly from the germ epithelium. There is a 

 reciprocal growth of vascular connective tissue and germ 

 epithelial cells, in consequence of which large and small 

 masses of the latter become imbedded more and more in the 

 stroma of the ovary. The imbedded cells present a variety. 

 Some of them, by simple increase in size, grow into ova, 

 viz. primordial ova, while others keep to their original size, 

 and by numerous divisions, at least as it appears to me, 

 produce still smaller cells, viz. the follicular epithelial cells. 

 A genetical distinction between primordial ova and follicular 

 epithelial cells has consequently no existence. The germ 

 epithelium is the common source of both." 



In describing the ovary of a newly born child, Waldeyer 

 thus states, in reference to its tubular structure : 



" One sees long branching formations in the form of tubes, 

 anastomosing with each other, as Valentin first described, 

 and lying separate from each other at considerable distances. 

 They pass upwards opening with narrow mouths into the 

 epithelium, and appear as direct tubular gland-like processes 

 of it. 



"At the time at which the tubes described by Pfliiger 



^ " Ueber die Entwickelung der rollikel in dem Eierstock der Saiige- 

 thiere," ' J. Miiller's Archiv. fiir Anat. u. Physiol.,' 1838. 

 ^ ' Die Eierstocke der Saiigethiere und des Meuschen,' Leipzig, 1863. 



