410 INTERNAL SECRETIONS 



extent to which the tissues of the two sexes differ must vary 

 in different animals and in respect of different characters; in 

 birds . . . the difference must be considerable, while in mammals 

 Steinach found that each sex could be made to assume to a 

 very great extent the characters of the other by cross-grafting 

 of ovaries and testes." The experiments of Goodale, Pezard 

 and Zawadowsky have shown that there is in this matter no 

 difference between mammals and birds. I think that it is 

 impossible to draw any general conclusions opposed to the 

 theory that the sex characters are conditioned by sex specific, 

 hormones from the observations on birds with lateral inter- 

 sexuality. It is not impossible that the condition is caused 

 by an hormonic intersexuality complicated by some other 

 abnormality. I have pointed out that possibly some abnor- 

 mality in the distribution of the blood vessels during embryonic 

 development might be one of the causes of lateral inter- 

 sexuality. It suffices to recall the important role played by 

 the abnormal distribution of the blood vessels in conditioning 

 the development of the freemartin. On the other hand, I 

 have considered the possibility of an hormonic intersexuality 

 complicated by some other teratological condition, an hormonic 

 and a somatic abnormality being coincidently present. On more 

 or less similar lines, Pezard (1922 b) has lately elaborated in 

 detail a theory explaining lateral intersexuality in birds. His 

 starting point is the assumption that there is a coincidence of 

 two different abnormal conditions, a somatic and an hormonic 

 one. Normall}^ both sides of the body react to the threshold 

 quantity of female hormones in a similar manner, and female 

 plumage develops likewise on both sides. But now suppose 

 with Pezard that the threshold quantit}^ is abnormally high 

 for one side, and that at the same time only the threshold 

 quantity of female hormones is produced in this individual. 

 A lateral intersexuality as to plumage will result, since the 

 quantity of hormones produced will be able to feminize only 

 that side of the animal which is normal, whereas the abnormal 

 side will reveal the neutral plumage, which is almost identical 

 with the male one. Pezard, Sand and Caridroit (1923 a, 1923 b) 

 have induced experimentally lateral intersexuahty in birds by 

 plucking the feathers of the back and tail of a Leghorn cock 

 on one side in December, and engrafting an ovary into the 

 testicle. In about six weeks a new plumage appeared, which was 



