422 



THE PINEAL ORGAN 



Pinealectomy 



Assuming that the pineal organ exerts an inhibitory influence on body 

 growth and the development of the sexual organs, perhaps the most 

 striking positive results which have been obtained in support of this 

 view were those described by Foa in 19 12 and Izawa in 1922. Foa per- 

 formed the difficult operation of removing the pineal gland in young 

 chicks between the ages of 5 and 7 weeks. The mortality was large and 

 only a small number of chicks survived. After a period of 3 months 

 the latter showed that the general development of the body had been 

 much more rapid in the experimental birds than in the controls, and also 



Fig. 282. — A — Crest, and B — Testicle of a Cock from which the Epiphysis 

 had been removed three months previously ; a — crest, and b — testicle 

 of a Normal Control Specimen of the Same Age. 



The development of the experimental animals was much more rapid than the 

 controls, and the development of the secondary sexual characters (crow, crest, 

 spurs) was equally precocious. 



(After Foa ; redrawn from UEpiphyse, J. Calvet.) 



that the development of the secondary sexual characters had been more 

 precocious and active in the experimental animals, namely, the growth of 

 the comb and spurs and the early occurrence of crowing (Fig. 282). 

 Moreover, at the age of 10 to 12 months Foa examined the testicles of the 

 pinealectomized birds and found that they were not only increased in 

 size, but also showed that the general increase was due to the hypertrophy 

 of both the interstitial tissue and the seminiferous tubules. He obtained 

 similar results by repeating these experiments on rats and mice and 

 another series of young chicks. In the latter series he noted that the 

 size was not so markedly influenced as in the first series, and also that 

 pinealectomy had no effect on hens. 



