638 THE PHYSIOLOGY OF REPRODUCTION 



of oestrus and an increased number of litters (see p. 46). In a 

 similar way long-continued lactation is believed to reduce the 

 fecundity of women, who sometimes refrain from weaning their 

 babies in the belief that by so doing they are less liable to become 

 pregnant again. Moreover, Haddon's observations l upon the Eastern 

 Islanders of the Torres Straits show that with these people also 

 prolonged nursing tends to reduce the size of the families, and that a 

 single lactation may be continued for three years 



EFFECT OF DRUGS 



There is little evidence as to the effects of drugs upon egg- or 

 sperm-production, but innumerable substances have been recom- 

 mended as cures for impotence. 2 Cantharides and various other 

 drugs are said to produce sexual excitement, but this result is 

 probably due simply to the increased flow of blood to the generative 

 organs which these substances induce. 3 Wallace says that the 

 practice adopted by some grooms of giving cantharides to stallions is 

 strongly to be deprecated. Bloch is disposed to recommend the use 

 of phosphorus and strychnine in the treatment of impotence in men, 

 but the most favourable results have been obtained by yohimbine, 

 an alkaloid prepared from the bark of a West African tree. Bloch 

 mentions several cases where, in his own experience, treatment by 

 yohimbine has been entirely successful, and there are numerous 

 others on record. Many 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 4 found that yohimbine when administered to dogs 

 produced hypertemia of the generative organs, followed by mucous 

 and sanguineous discharge, but not true heat. Dr. Cramer and the 

 present writer 5 have made similar observations. We first 

 administered O'OOS gram of yohimbine twice daily for nearly a 

 fortnight to each of two anoestrous bitches, the drug been swallowed 

 in the form of tablets. Marked congestion of the generative 

 organs followed. On treating rabbits with yohimbine the vulva 

 and the uterine mucosa became excessively hypersemic, the entire 



1 Haddon, Reports of the Cambridge Anthropological Expedition to Torres 

 Straits, vol. vi., Cambridge, 1908. 



2 For the distinction between sterility and impotence see below (p. 644). 

 For detrimental results of drug action or abnormal treatment on sperm- or 

 egg-production see also below (p. 647). 



3 Bloch, The Sexual Life of our Time, English Translation, London, 1908. 



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

 Gynaecology and Obstetrics, vol. vi., (February) 1908. 



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

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



