726 



SPERM, OVA, AXD PREGNANCY 



2Z0 



210 



en 200 



X 



£ 

 E 

 I 190 



LJ 



cr 



z> 



^ 180 



if) 



LlJ 



cr 



CL 



170- 



160 



150 



140 



WITHDRAWAL 



8 

 MINUTES 



10 



16 



Fig. 13.6. Blood pressure of dog during coitus. (After L. M. Pussep, Der Bhitkreidauj im 

 Gehirn beini Koitus, Dorpat, 1921.) 



TABLE 13.5 



Volume and sperm density of mammalian ejaculates 

 (From T. Mann, Advances Enzymol., 9, 329-390, 

 1949; S. A. Asdell, Patterns of Mammalian Re- 

 production, Comstock Publishing Co., 1946.) 



of the respective accessory glands determine 

 the quantity of semen in the ejaculate. The 

 volumes of seminal discharge from several 

 mammals are presented in Table 13.5. The 



enormous volume of the boar ejaculate, as 

 much as half a liter, may be of importance 

 in "washing" the sperm through the uterus, 

 inasmuch as in the sow the semen is de- 

 posited directly into the cervix, and the 

 ejaculate is so proportioned that the sper- 

 matozoa are concentrated in the earlier frac- 

 tions and are followed by a copious flood of 

 relatively sperm-free fluid (McKenzie, Mil- 

 ler and Bauguess, 1938) . When fractional 

 collection is possible, the spermatozoa are 

 found generally concentrated in the initial 

 or middle portion of the ejaculate (ram, dog, 

 boar, horse, and man). The ejaculate of the 

 dog consists of a small, initial, clear, rela- 

 tively sperm-free portion, followed by a 

 milky fraction containing the bulk of the 

 spermatozoa, and finally a slow but copious 

 dribble largely derived from the prostate 

 (Evans, 1933; Hartman, unpublished data). 

 Collection by means of the electrically stim- 

 ulated "split-ejaculation" technique has 



