432 Pork Production 



loin just in front of and below the kidneys. When the 

 eggs are ripened, they drop into the upper end of the Fallo- 

 pian tubes and, through gravity, finally reach the womb 

 or uterus. The outward manifestations of these func- 

 tional activities are called "heat." The male germ-cells 

 or sperms are secreted by the testes, the essential part of 

 the testicles, corresponding in function to the ovaries of 

 the sow. For every egg produced by the sow, the boar 

 produces many thousands of sperms. The number of 

 sperms contained in a cubic millimeter of semen from a 

 normal boar runs from 6000 to 600,000,^ depending on 

 his natural vigor and the distribution of the services. 

 The average number produced in an isolated service is 

 about 450,000 to a cubic millimeter. At this rate a tea- 

 spoonful of semen would contain 3,600,000 sperms. 



The female germ-cells or eggs are relatively large com- 

 pared with the male germ-cells or sperms. Although too 

 small to be visible with the naked eye, the eggs are several 

 thousand times larger than the sperms. The sperms are 

 extremely minute, measuring x^ of a millimeter in length, 

 which would require that 482 be laid end to end to measure 

 one inch. The large size of the egg compared with the 

 sperm does not mean that the sow contributes a larger 

 hereditary influence to the pigs than does the boar, but 

 only that the food supply (egg-yolk) necessary to sustain 

 the life of the fertilized egg until conception is complete, 

 is carried in the egg. 



The shape of the egg is spherical like a ball, while the 

 sperm is elongated, consisting of a head, middle, and tail 

 piece, very much resembling a tadpole in appearance. 

 While the egg is passive, the live sperm is active and ca- 

 pable of locomotion. This is accomplished by the rapid 

 ' L. L. Lewis, Okla. Exp. Sta. Bull. 96. 



