THE FEMALE REPRODUCTIVE ORGANS. 843 



swollen and in many animals there is a discharge of mucus or 

 mucus and blood from the uterus. Histologically the mucous mem- 

 brane of the uterus undergoes changes similar to those of menstrua- 

 tion, that is, the membrane increases in size and becomes con- 

 gested with blood, and it exhibits a phase of degeneration 

 during which some of the epithelial lining may be cast off and some 

 hemorrhage occur. If sexual union is prevented during this period 

 heat passes away in a few days, but recurs again at intervals 

 which vary in the different mammals: 4 weeks in the monkey, 

 mare, etc.; 3 to 4 weeks in the cow; 2J to 4 weeks in the sheep; 

 9 to 18 days in the sow; 12 to 16 weeks in the bitch, etc. The re- 

 currence of the period under these circumstances suggests at once 

 the essential resemblance to the monthly periods of women. Ac- 

 cording to Heape's most interesting observations upon monkeys 

 (Semnopithecus),* some of these animals show a regular monthly 

 flow lasting for 4 days except when conception takes place. The 

 changes during heat must be considered as physiologically ho- 

 mologous to those of menstruation. The sexual excitement that 

 attends the condition in the lower animals is not distinctly repre- 

 sented in man, although it is commonly said that in the period pre- 

 ceding or following menstruation the sexual desire is stronger than 

 at other times, but in the changes undergone by the uterus and the 

 fact that these changes are connected, as a rule, with the liberation 

 of an egg from the ovary (ovulation) the two phenomena are 

 physiologically similar. 



Relation of the Ovaries to Menstruation. It appears to be 

 clearly demonstrated that the phenomenon of menstruation is de- 

 pendent upon a periodical activity in the ovaries. When the 

 ovaries are completely removed menstruation ceases (artificial 

 menopause) and the uterus undergoes atrophy. When the ovaries 

 are congenitally lacking or rudimentary, a condition of amenorrhea 

 also exists. These facts and the connection of the ovaries with 

 menstruation are further corroborated in a striking way by experi- 

 ments upon transplantation or grafting of the ovary. This experi- 

 ment has been performed upon lower animals (apes) as well as upon 

 human beings. Removal of both ovaries in apes is followed by a ces- 

 sation of menstruation. Transplantation of an ovary under the skin 

 serves to maintain menstruation, but if subsequently removed this 

 function disappears. f In the human being Morris and Glass ob- 

 tained similar results. J: An ovary or a piece of an ovary trans- 

 planted into the uterus itself or the broad ligament caused a re- 



*Heape, "Philosophical Transactions, Royal Society," 185 (B), 1894, 

 and 188 (B), 1897. 



t Halban, "Deutsche Gesellschaft f. Gynakol.," 9, 1901. 



j Glass, "Medical News," 523, 1899; Morris, "Medical Record," 83, 

 1901. 



