Discussion 29 



the experimental analysis of the temporal phases of development you 

 do not attempt to derange the whole system in time. In fact, we do not 

 know a priori that the cells of some target tissue mature at a given stage 

 and that they can only react at a given point to some endocrine stimu- 

 lation. This constitutes deduction from experimental results. 



Huggett: A positive result from Prof. Zuckerman's experiment would 

 be very interesting; a negative result would not disprove anything else 

 Jost: Concerning the physiology of the liver, the point raised by 

 Prof. Zuckerman can be studied on decapitated foetuses given ACTH. 

 Is ACTH able to induce the liver to store glycogen earlier than usual? 

 In a short series of cases we did not observe anything like that. Is 

 ACTH still able to act at late stages on the liver of early decapitated 

 foetuses which did not store glycogen in the right time? We have only 

 a few trial experiments which are not yet conclusive. Such experiments 

 still have to be done. 



Rowlands: What are the gonadal effects of decapitation at this stage? 

 Are there any changes that would suggest the action of a gonadotrophin ? 

 Jost: In the testes, the interstitial cells do develop but on day 28 they 

 are reduced in decapitates and enlarged when gonadotrophic hormone is 

 given. Moreover, the genital tract is a good indicator of their activity; 

 before day 22 or 24 it develops normally in decapitates. 



Huggett: Prof. Jost, have you controlled your decapitation by merely 

 transecting the cord leaving the head on ? It seems to me that you have 

 not absolutely proven that this might not be a neural effect. 



Jost: I tried not exactly that experiment but some other ones. I tried 

 to graft a pituitary gland onto a decapitated foetus and I studied the 

 genital tract. I had only four cases of such grafts on males. In these 

 four cases, I had one positive case in which the decapitated foetus 

 had a normal genital tract, another case which was doubtful, and two 

 cases which were negative. So I should not like to give too much 

 importance to these preliminary observations, but I feel that if it 

 were possible to replace the whole head by a grafted pituitary gland the 

 demonstration would be good enough. 



Huggett: A series of positive results would be interesting; negative re- 

 sults might be defective surgery. But I would like to see what happened 

 if, instead of actually decapitating, you inserted, say an iridectomy 

 knife, and just transected the cord level with the first cervical, the normal 

 place for spinalizing an animal, sew the wound up and return the total 

 foetus instead of the decapitated trunk. 



Jost: This is an interesting suggestion. In the past I tried another 

 experiment of this type, by removing the brain and the bulb and leaving 

 the pituitary gland in place. The result was not a success because the 

 pituitary gland was ill-developed, although not completely necrosed. 



Dawes: I was going to ask about the nervous system from the point 

 of view of the circulation. I would not expect any very great alteration 

 if the head was removed up to half-way through pregnancy. I do not 

 know what happens in rabbits, but in sheep the nervous control of the 

 circulation becomes increasingly important towards the end of preg- 

 nancy, and I wondered whether some of the results you obtain towards 



