B. A. HOUSSAY 



complex functional mechanisms. Thus, the regulation of the metabo- 

 lism of carbohydrates involves the liver, insuHn, hypophysial, cor- 

 ticoadrenal, and thyroid hormones, as well as participation of the in- 

 testine, kidney, and muscle. Sexual functions depend upon the com- 

 bined action of the hormones of the hypophysis, ovary, corpus luteum, 

 and placenta (during pregnancy), plus the action of still other glands, 

 such as the adrenal cortex and the thyroid. 



As explained further on, in any single function of the organism 

 more than one hormone plays its part, even when one of them exhibits 

 a very specific and preponderant role. 



(4) Sexuality and Reproduction. — Among the endocrine actions, 

 the sexual functions are especially important. These functions depend 

 on the hormones of the gonads, governed in part by the pituitary go- 

 nadotropins, in part by the hormones of the adrenal cortex and, to a cer- 

 tain degree, by the thyroid. They regulate the production of the fe- 

 male (ovule) and male (spermatozoid) germinal cells or the develop- 

 ment of the organs which carry them, the development of the impulses 

 and sexual acts that lead to fecundation, the progress of pregnancy and 

 delivery, and the secretion of milk. The sexual hormones are mdis- 

 pensable links for individual sexuality and for the maintenance of the 

 species. 



(5) Mental and Nervous Functions. — The hormones influence 

 several nervous and muscular activities. We only need to remember 

 the differences shown by the sexes, the mental dullness due to hypo- 

 thyroidism, the nervousness or mental instability of hyperthyroidism, 

 the tetany of hypoparathyroidism, etc. These actions of the hormones 

 are probably due to their influence on the metabolism of the nervous 

 system, a point that has not received much study. 



(6) Vital Role. — The extirpation of some endocrine glands 

 causes death. This was attributed to hypothetical poisons which ac- 

 cumulated because they were not neutralized by the endocrine glands 

 (antitoxic role), a theory that has been abandoned because no poison 

 has been demonstrated and because it has been proved that death 

 was due to metabolic disturbances provoked by the lack of the hormones 

 normally produced by the organ in question. 



(7) Resistance. — The hormones are important factors in build- 

 ing up the resistance of the organism to certain hazards such as high or 

 low temperatures, low or excessive oxygen tension, overexercise, in- 



