276 PRINCIPLES OF STOCK-BREEDING. 



ence to the ovary itself, as well as to the germs that 

 are not fully developed. 



During the period of heat in the lower animals, 

 and of menstruation in women, one or more germs are 

 matured and escape from the ovary, so that the term 

 periodical ovulation has been used to designate the 

 process. 



"When a germ is thus liberated the walls of the 

 follicle that contained it become thickened, and a pe- 

 culiar cicatrix is formed, which is called the corpus 

 luteum. If impregnation of the germ has not taken 

 place, the corpus luteum attains its maximum of de- 

 velopment at the end of three weeks (measuring three- 

 fourths of an inch in length and one-half inch wide), 

 and then gradually diminishes in size, so that a minute 

 cicatrix remains at the end of seven or eight weeks, 

 and in the course of seven or eight months it entirely 

 disappears. 



"When the germ is impregnated the corpus luteum 

 attains a greater development, continuing its growth 

 to the end of the fourth month, when it measures 

 seven-eighths of an inch in length, and three-fourths 

 of an inch in depth. 



During the fifth and sixth months it remains un- 

 changed, but diminishes again during the seventh, 

 eighth, and ninth months, when it measures half an 

 inch in length and three-eighths of an inch in depth. 

 Several months after delivery the corpus luteum en- 

 tirely disappears. 1 



The mere fact of impregnation seems to determine 



1 Dalton's " Human Physiology," pp. 664-573 ; Flint's " Physiology 

 of Man," vol. v. (" Generation"), pp. 307-312. 



