30 Discussion 



the end of pregnancy in the rabbit might not be a result of alterations 

 of the internal environment in that way. That was one point and the 

 other was this. Ashton, Ward and Serpell (1953)* have shown that, 

 at certain stages of development of the retinal vessels, constriction 

 caused by excess oxygen leads to obliteration from mal-development in 

 newborn kittens. Perhaps if you were to inject pitressin into foetal 

 rabbits at a certain stage of development, their fingers might fall off or 

 fail to develop, simply because at that critical stage there may be con- 

 striction and hence clotting in the peripheral vessels ; that is, simply a 

 vascular effect, and not what we usually think of as a hormonal effect 

 upon cells. 



Jost: First, concerning the effect of pitressin or other hormones pro- 

 ducing necrosis and congenital amputations of the extremities of the 

 foetus : the final explanation of the haemorrhages involved has still to 

 be found. A careful study of the vessels and measurement of blood 

 pressure is needed. 



Finally, the technique of decapitation should not be considered as the 

 final ne plus ultra technique in foetal endocrinology. It was useful and 

 still remains of interest since it put on an experimental status questions 

 which were discussed before in a more or less speculative manner. Now 

 we know that correlations exist between the head and several endo- 

 crines. It has not yet been absolutely demonstrated that the nervous 

 system is not involved, but the fact that the appropriate pituitary 

 hormone may replace the head indicates at least that the nervous 

 system is not indispensable. The concomitant changes noted in the 

 pituitary gland and in the other endocrine glands afford another argu- 

 ment in favour of the hormonal interpretation. 



* Ashton, N., Ward, B., and Serpell, G. (1953). Brit. J. Ophthal, 37, 513. 



