208 SEXUAL GENERATION. 



peds measures about one, one hundred and twentieth of an inch in 

 diameter. These eggs exist primarily in the organs of an animal as a 

 part of their natural organization. Their essential constituents are of 

 the same peculiar qualities, and the process of development follows the 

 same general laws in all nature. In the lower animals, as the genera- 

 tive season draws near, a certain number of eggs, which were previously 

 but partially formed and inactive, grow larger and undergo structural 

 changes. They ripen, as it were, distending the follicles, and finally, 

 when fully matured, the inclosing walls are ruptured and they are dis- 

 charged into the oviducts. When simply expelled from the ovary and 

 conveyed through the oviducts towards the external genitals, the matured 

 egg soon loses its vitality and becomes decomposed. It is not of itself 

 capable of being developed into the embryo, and is only rendered fruit- 

 ful by the germ of the opposite sex. When the seminal fluid of the male 

 is introduced into the female generative passages by sexual congress and 

 meets the egg at or near its discharge from the ovary, it causes its reten- 

 tion, stimulates it to continued development, and renders it capable of a 

 more complete organization. 



(ESTRUATION. 



The ripening and discharge of the egg from the ovary are attended by 

 a peculiar state of the entire system known as the "rutting" condition, or 

 cestruation. The congestion and increased activity of the ovaries, at each 

 period of ovulation, act by sympathy upon the accessory generative or- 

 gans, producing in them a certain degree of excitement and irritation. 



In the bitch the mucous membrane of the vagina and external genitals 

 becomes red and swollen, the secretions, more abundant, are first tinged 

 with blood and acquire a peculiar odor which attracts the dog and excites 

 him to sexual impulse. The discharge deepens in color and finally be- 

 comes a bright red and of the appearance of clear blood. 



The amount of swelling of the vulva varies : in some cases it is very per- 

 ceptible, affecting the neighboring tissues. During the first week the 

 swelling is hard and tense, then less resisting to the touch, softening as it 

 were. In the second week the discharge subsides somewhat, becomes 

 lighter in color and finally colorless. Generally between the twelfth and 

 fourteenth day the bitch will allow the approaches of the dog. 



During a period of from four to seven days this disposition continues, 

 and by her unusual excitement and manner she invites sexual concourse. 



