BREEDING. 129 



modically (reflexly) grasped by the muscles {sjpliincter 

 cimni) of the vagina, so that the male organ can not be 

 withdrawn until erection subsides. Since certain glands 

 {Cow;per^s) that secrete diluting fluids are wanting in the 

 dog, as well as the reservoirs {seminal vesicles) in which 

 in many animals semen is stored up, the importance of 

 this arrangement enforcing prolonged copulation can be 

 understood. 



The forcible separation of dogs in coitu maiy lead to 

 rupture of parts and dangerous bleeding. 



The whole period of being in "heat," "in season," 

 or " in use " extends over about three weeks, but often 

 longer, and of course in a minority of cases less. During 

 the whole of this period, as a rule, it is of the greatest im- 

 portance to keep the bitch entirely separate from all dogs 

 except the one selected. The sexual appetite of bitches is 

 strong and persistent, and no risks should be taken. 



The meeting of male and female cells usually results 

 in impregnation or that commingling of their parts which 

 results in the division {segmentation) of the female cell 

 (egg, ovum) and its whole growth and development. 

 Strictly speaking, however, we should say that the two 

 are blended for growth, etc. If this were more carefully 

 kept in mind the whole subject of breeding might be dis- 

 cussed in a more intelligent manner. 



The two united cells making up the as yet undevel- 

 oped individual soon provide arrangements for receiving 

 nourishment from the mother and getting rid of the waste 

 of their own life-processes. This is accomplished by cer- 

 tain outgrowths which develop into the placenta, which 

 may be finally said to consist of two parts — a maternal and 



