796 



NA TURIi 



[December i, 1923 



im[)l.mtation of ovaries or testes into the foetus at a 

 Mill i.ntlv early age, one could produce the whole 

 tl< ii of the internal and external genitalia 



c(. aji to the sex of the gland implanted. 



h »> worthy of note that these sex characters affect 

 also the mentality and the reactions of the animal, 

 although they arc (juite independent o( any nervous 

 connexions. Here, as in the case of the thyroid, the 

 functions of the central nervous system in their highest 

 manifestations de|)end on the circulation in the blood 

 of chemical substances or hormones. The wonderful 

 development that takes place in the female after 

 conception to fit her to nourish the fcetus as well as 

 the young child, is also due to hormones, produced 

 in some cases perhaps in the ovaries, in other cases 

 in the product of conception itself. 



We owe to Schafer the knowledge of the internal 

 secretion of the medulla of the suprarenal bodies. 

 As Cannon has pointed out, this secretion is poured 

 into the blood during conditions of stress, anger, or 

 fear, and acts as a potent reinforcement to the energies 

 of the body. It increases the tone of the blood vessels, 

 as well as the power of the heart's contraction, while 

 it mobilises the sugar bound up in the liver, so that 

 the muscles may be supplied with the most readily 

 available source of energy in the struggle to which 

 these emotional states are the essential precursors or 

 concomitants. 



Wonderful, too, is the intiuence exerted by the 

 secretions of the pituitary body. This tiny organ, 

 which was formerly imagined to furnish the mucus 

 to the nasal cavities, consists of two lobes which have 

 different internal secretions. That produced by the 

 anterior lobe seems to influence growth, excess pro- 

 ducing gigantism or acromegaly, while deficiency leads 

 to retarded growth and infantilism. The posterior 

 lobe, which in aspect would seem but a small collection 

 of neuroglia, nevertheless forms one or more substances 

 which, circulating in the blood, have the most diverse 

 influences on various parts of the body. They cause 

 contraction of the uterus and of the blood-vessels 

 (these are possibly two distinct substances) ; they 

 may increase or diminish the flow of urine ; they 

 affect the excretion of chlorides by the kidney ; and, 

 according to Krogh, their constant presence in the 

 blood is essential for maintaining the normal tone 

 of the capillaries. In the frog the post-pituitary 

 hormone is responsible for the protective adaptation 

 of the colour of the skin to the environment, an adapta- 

 tion which is effected by retraction or expansion of 

 the pigment cells or chromatophores of the skin ; and^ 

 if we may accept Kammerer's conclusions, the pituitary 

 hormone which is poured into the blood for this purpose 

 affects the germ cells themselves, so that individuals 

 bom of parents that have lived in light or dark sur- 

 roundings are correspondingly light or dark — a real 

 transmission of acquired peculiarities, effected not by 

 the gemmules of Darwin, but by the influence of a 

 soluble diffusible hormone on the germ plasm. 



In the multiplicity and diversity of the physiological 

 effects produced by these various chemical messengers, 

 one is apt to lose sight of the fact that we are here 

 investigating one of the fundamental means for the 

 integration of the functions of the body. These are 

 not merely interesting facts which form a pretty story, 



NO. 2822, VOL. I 12] 



but they are pregnant of possibilities for our contrJ 

 of the processes of the body and therewith for our 

 mastery of disease. Already medical science can 

 boast of notable achievements in this direction. The 

 conversion of a stunted, pot-l)cllied, slavering cretin 

 into a pretty, attractive child by the administration 

 of thyroid, and the restoration of normal heiilth and 

 personality to a sufferer from Graves's disease by the 

 removal of the excess of thyroid gland, must always 

 impress us as almost miraculous. In the same way 

 we may cure or control for the time being diabetes 

 insipidus by the injection of the watery extract of 

 the posterior lobe of the pituitary body. The latest I 

 achievement in this direction is the preparation by ■ 

 Banting and Best in Canada of the active principle 

 normally formed in the islets of the pancreas, and the 

 proof that the diabetic condition in its severest forms 

 can be relieved by its subcutaneous administration. 



In my Croonian Lectures I asserted that, if a mutual 

 control of the different functions of the body be largely 

 determined by the production of definite chemical 

 substances in the body, the discovery of the nature 

 of these substances will enable us to interpose at any 

 desired phase in these functions, and so to acquire 

 an absolute control over the workings of the human 

 body. I think I may claim that, in the eighteen years 

 that have since elapsed, we have made considerable 

 progress towards the realisation of this power of 

 control which is the goal of medical science. But 

 there still remain much to be done and many diffi- 

 culties to be unravelled, and it may be worth our while 

 to consider along what lines researches to this end 

 must be directed. 



There are no doubt many hormonic relationships 

 of which at present we are unaware, since every year 

 research adds to their number. But assuming we 

 know that such and such an organ produces an internal 

 secretion which is necessary for the normal carrying 

 on of a given function or functions, we may desire 

 to diminish or enhance its effects in a patient or to 

 replace it when it seems to be entirely lacking. There 

 seem to be three possible methods by which we medical 

 men can interpose our art in the hormonic workings 

 of the body. 



(i) In the first place, we may find what is the effective 

 stimulus to the production of the hormone, and, by 

 supplying this, increase its production by the responsible 

 cells. For example, we know that by the administra- 

 tion of acid, or at any rate by increasing the passage 

 of weak acid from the stomach to the duodenum, we 

 can enhance the production of secretin and so of 

 pancreatic juice and the other juices. Probably, 

 therefore, when we give dilute acids to assist gastric 

 digestion we are setting into motion the whole chain 

 of reflex processes in the alimentary canal, and the 

 chief value of our administration may be its effect 

 on the pancreas. But in a large number of cases we 

 do not yet know what is the effective stimulus to the 

 production of these internal secretions. In the case 

 of the adrenals we know the secretion can be augmented 

 through the central nervous system and the splanchnic 

 nerve under the influence of emotions or of lack of 

 oxygen, but we have no knowledge of the factors 

 determining the production of the pituitan.' hormones 

 or of insulin by the islets of Langerhans, and this 



