44 THE BREEDING OF ANIMALS 



is immediately over the cup-shaped depression just in 

 front of the cervix. The semen is then drawn into the 

 syringe and the instrument introduced into the vagina 

 of the mare to be artificially bred and pushed carefully 

 through the neck of the womb to insure the depositing 

 of the semen inside the uterus. Care should be taken 

 not to introduce the point of the syringe into the opening 

 to the bladder which is only five or six inches from the 

 external opening of the vagina. The transfer of the 

 semen to the waiting mare should be made without un- 

 necessary delay and all instruments should be kept at 

 body temperature during the operation. All instruments 

 should be thoroughly sterilized in hot water before using. 



Many interesting questions of biological and practical 

 interest are raised by the practice of artificial insemina- 

 tion. How long after the semen is collected will it con- 

 tinue to be potent? What external conditions such as 

 cold, heat, light and air affect the vitality of the germ? 

 How long does the semen retain its vitality within the 

 reproductive organs of the female? Partial answers 

 to these questions have been given through the investi- 

 gations of Lewis. 1 



45. Conditions influencing the vitality of the sperm- 

 cells. The vitality of semen collected and preserved 

 at different temperatures under laboratory conditions 

 showed great variations. High temperatures were gen- 

 erally unfavorable. At the end of one hour the percentage 

 of semen which was alive and active was : at 33 C., 40 

 per cent ; at 30 C., 45 per cent ; at 26 C., 85 per cent, and 

 at 18 C., 90 per cent. At the end of two-and-one-half 

 hours all the sperm-cells maintained at the temperatures 

 of 33 C. and 39 C. were dead, while 65 per cent of the 



1 Lewis, Oklahoma Experiment Station, Bulletins 93 and 96. 



