1 88 Discussions 



inserted into ihe posterior hypothalamus, activated mating behavior in female cats. 

 Similar implants in other parts of the brain did not produce this result. Since cats with 

 mammillary body implants showed sustained mating behavior in the presence of 

 persistently anestrous genital tracts, it was concluded that the hormone action was 

 local and not general. Dr. Sawyer has, 1 know, found evidence that the region of the 

 hypothalamus involved with sexual behavior in the cat lies more anteriorly. What 

 the answer here is I don't know. The only thing that strikes me in this connection, and 

 this 1 have discussed before with Dr. Sawyer, is that the production of a positive 

 response by some experimental procedure involving the hypothalamus is probably 

 more significant than the loss of a response. The hypothalamus is obviously concerned 

 with many autonomic and endocrine functions. Therefore, the loss of a particular 

 behavior pattern following a hypothalamic lesion might be brought about in many 

 indirect ways, such as through failure in food intake, loss of control of body temperature 

 or blood pressure, and so on. On the other hand the excitation of a behavioral pattern 

 when it would not otherwise be present is probably much more specific. 



Dr. Ernest Knobil: Mr. Hammond described a cystic ovary which, if ruptured mechani- 

 cally, would undergo luteinization. Does this mean that there is normally a 

 decompression of the follicle when luteinization occurs under hormonal influence? 



Mr. John Hammond, Jr.: The experiments were my father's, on the cow. After rupture 

 of the cyst, you get another follicle to ovulate. You can induce this by injection of 

 pregnancy urine; or, if you manually rupture the follicle, then you get luteinization 

 of that same follicle. After luteinization, you can feel a great crack across the corpus, 

 instead of an ovulation point. 1 have done this myself. I feel that you may stimulate 

 a follicle to the point of being able to luteinize; but that luteinization may not follow 

 unless the pressure inside the follicle is released. 



I mentioned, I think, that when you express the corpus (following a PMS injection) 

 you may get luteinization of ruptured follicles. I have in one or two cases bruised 

 such a follicle and got a localized patch of luteal tissue in the wall of the follicle. 



Dr. Ernest Knobil: I think most of us believe the hormone acts directly on the granulosa 

 cells and transforms them into lutein cells. 



Dr. Roy O. Creep: I should like to ask Dr. Harris to elaborate a little more on his concept 

 of how the hypothalamic hypophyseal system works. He stated earlier that he makes 

 an extract of the median eminence and does not include the hypothalamus on the basis 

 that the active principle, whatever it might be, would thereby be diluted. 



1 should like 10 know how he visualizes the production of the active substance as 

 a product of the nerve endings of fibres emanating from somewhere in the hypo- 

 thalamus. I should like to know more about how this substance is produced in the 

 median eminence, if indeed it is produced there. Or, does it migrate from somewhere 

 in the hypothalamus? Surely, there must be some correction between the median 

 eminence and the hypothalamus. 



Dr. Geoffrey Harris: What I was trying to say this morning is this — the hypothesis is that 

 nerve tract(s) pass through the hypothalamus and have their termination on the 

 sinusoids of the primary plexus of the portal vessels in the median eminence. It is 

 supposed that at this site some humoral substance is transferred from the nerve 

 terminals into these vessels, and is then carried to the gland cells of the anterior 

 pituitary where it exerts a regulating influence. Such a hormonal substance might well 

 be present along the whole length of the nerve fibres, in the same way that acetylcholine 

 is known to be present along the whole nerve fibre in the case of cholinergic neurons. 

 It might then be argued that extracts of the hypothalamus would contain any active 

 material involved with these nerve tracts but, on the other hand, such material would 

 be expected to be greatly diluted by substances from nerve tissue adjacent to the tracts. 

 In the case of the median eminence, however, we have here a minute piece of tissue 

 in which the relative nerve tracts are focused. Wc might therefore expect to obtain more 

 concentrated extracts, weight for weight of nerve tissue, from this area. 



