GLANDS. 127 



zona pellucida) is about ^th of a line in thickness, 

 transparent, and entirely structureless. Its contents, 

 the vitellus or yelk, scarcely liquid in consistence, 

 contains a great number of very fine granules, pro- 

 bably fatty in their nature. At one point of the 

 periphery of the vitellus there is a brilliant spherical 

 nucleus, the germinal vehicle, or vesicle of Purkinje.* 

 Finally, the nucleus itself contains a nucleolus, called 

 the germinal spot ( Wagner). f 



Generally, as is well known, the ovisac contains but 

 one ovule ; nevertheless, it may contain two, as we 

 have seen in one instance, in the ovary of an adult (PL 

 XXI. fig. VII. 1, 2). We have also observed an 

 example of segmentation of the vitellus in another 

 ovum of the same female, which proves that this phe- 

 nomenon may take place in the interior of the ovary 

 without previous fecundation (fig. VIII). 



The Fallopian tube, or oviduct, which serves as the raiiopian tube. 

 excretory duet of the ovary after the detachment of 

 the ovum, has three layers of tissue in its walls ; the 

 first is serous, and belongs to the peritonaeum; the 

 next is composed of smooth muscular fibres and 

 blood-vessels ; the third is mucous membrane, the 

 surface of which presents longitudinal plaits, and is 

 covered by a single layer of cylindrical ciliated epi- 

 thelium. The vibratory motion of the cilia tends to 

 carry the contents of the tube onwards from without 

 inwards, and consequently facilitates the descent of 

 the ovum towards the cavity of the uterus. 



* Purkinje, Professor of Physiology in the University of Prague. (Ed.) 

 t Rudolf Wagner lately resigned the Chair of Physiology at the Uni- 

 versity of Gottingen, and was succeeded by Meissner. (Ed) 





