g2 INTRODUCTION TO SEXUAL PHYSIOLOGY 



chemical substances or hormones internally into the blood, and 

 that these act upon other and sometimes distant organs in the 

 body. In the experiments upon fowls the testes were removed 

 and sometimes broken up into numerous pieces, and these grafted 

 themselves on to the different parts of the peritoneum or on to the 

 outside wall of the gut, and the birds developed typical male 

 characters (growth of comb, wattle, etc., male voice, and sexual 

 and combative instincts). Such birds w^ere not capons but 

 typical cocks, excepting that they were unable to fertilise the 

 eggs in treading the hen (Foges, Shattock and Seligman, etc.). 

 So also wath the frog, Nussbaum showed that if the testes were 

 removed and one of them grafted into the dorsal lymph sac, the 

 musculature of the forearm underwent the usual hypertrophy, 

 and the clasping pad at the base of the second digit duly developed 

 at the onset of the breeding season. Experiments upon rats 

 have shown that if the testes be removed and grafted on to the 

 peritoneum or abdominal muscles, the prostate gland, vesiculse 

 seminales, and penis develop normally ; and similarly with 

 other animals. Moreover, the experiments of Steinach, Moore, 

 Sand, and others have shown that the transplantation of testes 

 from other individuals may promote the development of secondary 

 male characters in animals which were congenitally females, 

 and so the sex of the individual may be partially or almost 

 completely reversed. There are a large number of other experi- 

 ments wdth testicular grafts, which afford confirmatory evidence 

 of what is now regarded as an established fact that the testis 

 and (as we shall show later) the ovary are organs producing 

 internal secretions, and exert their influence through the inter- 

 mediation of the circulatory system. 



It is, of course, arguable that centripetal nerve fibres grow 

 into the grafted gonad, and that in this way a new path is 

 established leading to the central nervous system, but it w^ould 

 seem very unlikely that such a connection could be formed by an 

 organ in a quite abnormal position in the body. Injection 

 experiments, however, are not open to this criticism, but it 

 must be admitted that the evidence derived from these is still 

 somewhat inconclusive. Among the most satisfactory experi- 

 ments are those of Ancel and Bouin, who injected testicular 

 extract subcutaneously into castrated guinea-pigs over a period 

 of nine months, and found that the penis and vesiculse seminales 



