160 PHYSIOLOGY OF FARM ANIMALS [CH. 



the cat and rabbit ijrodiiced a powerful contraction of the muscles 

 of the vasa deferentia and related parts. Possibly more than one 

 centre is concerned in the jDrocess of ejaculation, but it is evident 

 that the one which presides over the muscular movements of the 

 internal generative organs is situated in the lumbar j^ortion of the 

 cord. 



The purpose of jjenile erection is to give the organ a sufficient 

 rigidity to make it possible to insert the organ into the vagina of 

 the female in the act of coition. In the stallion the erected penis 

 almost tills the vagina of the mare and a considerable amount of 

 friction occurs before seminal ejaculation is completed. In the 

 bull the end of the penis is more or less pointed and it is believed 

 that it is inserted into the mouth of the uterus. In the sheep the 

 filiform appendage is certainly projected into the os uteri. If 

 the appendage is cut off the ram is gejierally rendered bi^rren. 

 This fact is sometimes taken advantage of by ram traders when 

 wishing to discard tups for breeding purposes. The filiform 

 ajjpendage is removed before the ram is sent to market. Many 

 novices have been deceived by this ]3ractice, which is called 

 'worming'; for such rams are bought by luiscrupulous dealers 

 for a butcher's price in open market and then sold at a profit 

 as sound sires. 



In the dog the process of coition is different from that of most 

 mammals, and lasts for an unusually long time. This is due to the 

 fact that after the penis has been introduced into the vagina the 

 contraction of a sphincter in the female jorevents the withdrawal 

 of the organ until almost fully relaxed. 



The friction which is set up between the male and female 

 organs during coition causes a reflex discharge of motor impulses 

 in both sexes, the uterus undergoing a series of peristaltic con- 

 tractions. Thus Heape has described a sucking action on the part 

 of the uterus in the rabbit, the os uteri dipping down into the 

 seminal fluid at the bottom of the vagina to be withdrawn again 

 in correlation with a rhythmical contraction by the uterine 

 muscles. In the meantime the accessory sexual glands in the 

 female (Bartholini's glands, etc.) emit a secretion which is added 

 to the semen. 



Artificial Insemination. This method has been practised with 

 success on mares, cows and other domestic animals in order to 

 overcome certain forms of sterility in the female. It is only 



