B. A. HOUSSAY 



the secretions of a similar functional constellation (for example, the endo- 

 crine secretions which regulate sex or those that govern carbohydrate 

 metabolism, etc.)- These regulations are mainly humoral, depending 

 to a great extent on endocrine factors, although the nervous system 

 often has an important share. 



The tendency of the endocrine glands to reach a functional 

 equilibrium and then to maintain it without overshooting seems to con- 

 form to a sort of general law. Thus, when an ovary is extirpated, the 

 remaining ovary produces the same number of ovules and cycles 

 ("law of follicular constancy" of Lipschlitz). A testicular fragment 

 either assures the total development of the sexual characters of a cock, 

 or else it atrophies with no intermediate stable equilibrium being set 

 up (the "all or none" law of Pezard and Gley). The tendency to all 

 or none activity of the gland in situ, maintaining its secretion at a con- 

 stant level, independent of its mass, is not inconsistent with the fact 

 that the pharmacological effects of the hormones vary with the doses, 

 the relationship following the typical S-shaped curve. 



The close associations existing among the glands of internal 

 secretion explain why the disturbances affecting one of them are 

 generally reflected in the others. It is rarely, if ever, that experimental 

 or pathological disturbances of an endocrine organ are observed with- 

 out modifications of the other glands. Thus, the extirpation of the 

 hypophysis leads to atrophy and hypofunction of the adrenal cortex, 

 thyroid, and gonads. 



The actions of each hormone can be direct or indirect. The 

 testicle and androgenic hormones, for example, produce hypertrophy of 

 the seminal vesicles and prostate directly. The pituitary gonadotropin 

 (LH or ICSH) produces the same action, but since it induces the se- 

 cretion of testicular hormones is inactive in the absence of the testicle. 



In certain cases the functional interactions of endocrine glands 

 are simultaneous; in other cases they follow each other in sequence, 

 as the proliferative (estrogenic) and secreting (progesteronic) phases 

 of the endometrium during the menstrual cycle. 



HYPERSECRETION OF HORMONES 



That the secretion of the hormones is not normally at a maxi- 

 mum is borne out by several facts: {a) castration very much increases 

 the secretion of anterohypophysary gonadotropins: {b) adrenal 



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