:2tt8 OUTLINES OF EQUINE AXATOilY. 



sents a small amount of m.uscular structure in some parts 

 of its walls, and is lined with mucous membrane. There 

 is no doubt but that it secretes a special fluid to be added 

 to the semen. It also may, to a certain extent, serve as a 

 receptacle for retention of the semen until it is required 

 for use. 



The generative organs of the male produce the sperm- 

 cell, those of the female the germ-cell or ovum, and without 

 contact of these two cells reproduction cannot occur. The 

 ovum is produced in a special organ, one of which is 

 situated on either side of the spine in the lumbar region. 

 These are the ovaries or female testes. They are smaller 

 than the testes of the male and more rounded, and their 

 external surface is generally lobulated in consequence of 

 projection of certain vesicles which the organ contains. It 

 is invested by peritoneum, being situated at the anterior 

 part of the broad ligament of the uterus, and presents a 

 white fibrous stroma, tunica alhugmea, embedded in which 

 are certain vesicular bodies lined with tessellated epithe- 

 lium, and containing a quantity of albuminous fluid, in 

 which floats the ovum. These cysts receive the name 

 Graafian vesicles, and their lining membrane, which is 

 thickest at that part with which the ovum lies in contact, 

 is the memhrana granulosa. The ovum is a cell consisting 

 of a ceZ?-i6-a?/, zona pelliicida, and cell contents; the latter 

 consists of a nucleus or germinal vesicle, and a nucleolus 

 or germinal spot, floating in an albuminous fluid. 



The Graafian vesicles are sraallest at the centre of the 

 organ, and gradually increase in size on extending towards 

 the outer surface. By pressure they cause absorption of 

 the stroma, and thus at length bulge against the peritoneal 

 coat of the organ. Finally they rupture, thus discharging 

 their contents into the Fallopian tube. This occurs when 

 the animal is in "heat," as it is commonly termed, and 

 thus the ova commence their process of development into 

 the foetus. After rupture the Graafian vesicles become 

 filled with a mixture of blood and lymph, Vv'hich undergoes 

 contraction and organization until a stellate cicatrix, corpus 

 luteum, is produced, which is much more persistent when 

 its ovum has been impregnated than when it has under- 

 gone no further stage of development. These bodies 

 form our main guide in post-mortem decision, as to 

 whether an animal has ever been pregnant or not. 



