FERTILITY 601 



veterinarians also have testified to the powerful aphrodisiac 

 action of yohimbine, stating further that it is capable of inducing 

 a condition of heat in domestic animals and acting as an effective 

 remedy for certain kinds of sterility. 



Daels l found that yohimbine when administered to dogs 

 produced hypersemia of the generative organs, followed by 

 mucous and sanguineous discharge, but not true heat. Dr. 

 Cramer and the present writer 2 have made similar observations. 

 We first administered 0-005 grams of yohimbine twice daily for 

 nearly a fortnight to each of two ancestrous bitches, the drug 

 being swallowed in the form of tablets. Marked congestion of 

 the generative organs followed. On treating rabbits with yohim- 

 bine the vulva and the uterine mucosa became excessively 

 hyperaemic, the entire generative tract being affected to some 

 extent. The ovaries were much overgrown by luteal tissue, 

 and degenerate follicles which are generally so common in rabbits' 

 ovaries were relatively scarce. " It seems extremely probable, 

 therefore, that yohimbine, by preserving a constant and rich 

 supply of blood, and consequently of nutriment, to the ovaries, 

 may arrest the normal process of follicular degeneration, and so 

 be the means of bringing a larger number of follicles to maturity 

 than would otherwise be the case, thereby tending to increase 

 the fertility." There was some evidence also that yohimbine 

 may promote mammary development and the secretion of milk. 



EFFECTS OF IN-BREEDING AND CROSS-BREEDING 



The fact that in-breeding may result in a reduced fertility 

 has been already discussed in dealing with the significance of 

 the fertilisation process (pp. 207214). It was then pointed out 

 that a tendency towards sterility is often associated with a con- 

 stitutional loss of vigour. In the same place it was mentioned 

 further that cross fertilisation between organisms which are 

 allied but belong to different strains often results in an increased 



1 Daels, "On the Relation between the Ovaries and the Uterus," Surgery 

 Oyncecolofjy and Obstetrics, vol. vi. (Feb.), 1908. 



* Cramer and Marshall, " Preliminary Note on the Action of Yohimbine 

 on the Generative System," Jour. Econ. Biol., vol. iii., 1908. 



