September 5, 1912] 



NATURE 



17 



arteries and assists in the promotion of every action 

 which . is brought about through the s^-mpathetic 

 nervous svstem (Langle.v). In this manner the im- 

 portance 'of their integrity has been explained, 

 ahhough we have still much' to learn regarding their 

 functions. 



Thyroid. 

 Another instance of an internally secreting gland 

 which is essential to life, or at least to its maintenance 

 in a normal condition, is the thyroid. The association 

 of imperfect development or disease of the thyroid 

 with disorders of nutrition and inactivity of the nervous 

 svstem is well ascertained. The form of idiocy Icnown 

 as cretinism and the affection termed myxoed'ema are 

 both associated with deficiency of its secretion : some- 

 what similar conditions to these are produced by the 

 surgical removal of the gland. The symptoms are 

 alleviated or cured by the administration of its juice. 

 On the other hand, enlargement of the thyroid, accom- 

 panied by increase of its secretion, produces symptoms 

 of nervous excitation, and similar symptoms are caused 

 bv excessive administration of glandular substance by 

 the mouth. From these observations it is inferred that 

 the juice contains hormones which help to regulate 

 the nutrition of the body and serve to stimulate the 

 nervous system, for the higher functions of which 

 thev appear to be essential. To quote M. Gley, to 

 whose researches we owe much of our Ivnowledge 

 regarding the functions of this organ : " La genese 

 et I'exercice des plus hautes facultes de Thomme sont 

 conditionnes par Taction purement chimique d'un 

 produit de secretion. Que les psychologues meditent 

 ces faits ! " 



Paraihyro'xd.'s. 



The case of the parathyroid glandules is still more 

 remarkable. These organs were discovered by Sand- 

 strom in 1880. They are four minute bodies, each 

 no larger than a pin's head, imbedded in the thyroid. 

 .Small as they are, their internal secretion possesses 

 hormones which exert a powerful influence upon the 

 nervous system. If they are completely removed, a 

 complex of symptoms, technically known as "tetany." 

 is liable to occur, which is always serious and may be 

 fatal. Like the hormones of the thyroid itself, there- 

 fore, those of the parathyroids produce eflects upon 

 the nervous system, to w-hich they are carried by the 

 blood; although the effects are of a different kind. 



FiHntary. 

 Another internally secreting gland which has evoked 

 considerable interest during the last few years is the 

 pituitarv body. This is a small structure no larger 

 than a 'cob-nut attached to the base of the brain. It 

 is mainlv composed of glandular cells. Its removal 

 has been found (by most observers) to be fatal — often 

 within two or three days. Its hypertrophy, when 

 occurring during the general growth of the body, is 

 attended bv an undue development of the_ skeleton, 

 so that the stature tends to assume gigantic propor- 

 tions. When the hypertrophy occurs after growth 

 is completed, the extremities — viz., the hands and 

 feet, and the bones of the face — are mainly affected ; 

 hence the condition has been termed "acromegaly" 

 (enlargement of extremities). The association of_ this 

 condition with affections of the pituitary was pointed 

 out in 1885 by a distinguished French physician. Dr. 

 Pierre Marie. Both "giants" and " acromegalists " 

 are almost invariably found to have an enlarged 

 pituitarv. The enlargement is generally confined to 

 one part — the anterior lobe — and we conclude that this 

 produces hormones which stimulate the growth of 

 the bodv generally and of the skeleton in particular. 

 The reniainder of the pituitary is different in struc- 

 ture from the anterior lobe and has a different func- 

 KO. 2236, VOL. 90] 



tion. From it hormones can be e.xtracted which, like 

 those of the suprarenal capsule, although not exactly 

 in the same manner, influence the contraction of the 

 heart and arteries. Its extracts are also instrumental 

 in promoting the secretion of certain glands. When 

 injected into the blood they cause a free secretion 

 of water from the kidneys and of milk from the 

 mammary glands, neither of which organs are 

 directly influenced (as most other glands are) through 

 the nervous system. Doubtless under natural condi- 

 tions these organs are stimulated to activity by hor- 

 mones which are produced in the pituitary and which 

 pass from this into the blood. 



The internally secreting glands which have been 

 mentioned (thyroid, parathyroid, suprarenal, pituitary) 

 have, so far as is known, no other function than that 

 of producing chemical substances of this character 

 for the influencing of other organs, to which they 

 are conveyed by the blood. It is interesting to observe 

 that these glands are all of very small size, none 

 being larger than a walnut, and some — the para- 

 thvroids — almost microscopic. In spite of this, they 

 are essential to the proper maintenance of the life of 

 the bodv, and the total removal of anv of them by 

 disease or operation is in most cases speedily fatal. 



Vancrcas. 

 There are, however, organs in the body yielding 

 internal secretions to the blood in the shape of hor- 

 mones, but exercising at the same time other func- 

 tions. A striking instance is furnished by the 

 pancreas, the secretion of which is the most irn- 

 portant of the digestive juices. This — the pancreatic 

 juice — forms the external secretion of the gland, and 

 is poured into the intestine, where its action upon the 

 food as it passes out from the stomach has long 

 been recognised. It was, however,- discovered in 

 1S89 by von Mering and Minkowski that the pancreas 

 also furnishes an internal secretion, containing a 

 hormone which is passed from the pancreas into the 

 blood, bv which it is carried first to the liver and 

 afterwards to the body generally. This hormone is 

 essential to the proper utilisation of carbohydrates in 

 the organism. It is well known that the carbo- 

 hydrates of the food are converted into grape sugar 

 and circulate in this form in the blood, which always 

 contains a certain amount; the iDlood conveys it to 

 all the cells of the body, and they utilise it as fuel. 

 If, owing to disease of the pancreas or as the result 

 of its rernoval by surgical procedure, its internal secre- 

 tion is not available, sugar is no longer properly 

 utilised bv the cells of the body and tends to accumu- 

 late in the blood ; from the blood the excess passes 

 off by the kidneys, producing diabetes. 



.\nother instance of an internal secretion furnished 

 by an organ which is devoted largely to other /unc- 

 ti'ons is the " pro-secretin " found in the cells lining 

 the duodenum. \\'hen the acid gastric juice comes 

 into contact with these cells it converts their pro- 

 secretin into "secretin." This is a hormone which 

 is passed into the blood and circulates with that fluid. 

 It has a specific effect on the externally secreting cells of 

 the pancreas, and causes the rapid outpouring of pan- 

 creatic juice into the intestine. This effect is similar 

 to that of the hormones of the pituitary body upon 

 the cells of the kidney and mammarv gland. It was 

 discovered by Bayliss and Starling. 



Iniernal Secretions of the Reproductive Organs. 

 The reproductive glands furnish in many respects 

 the most interesting example of organs which — 

 besides their ordinary products, the germ- and sperm- 

 cells (ova and spermatozoa) — form hormones which 



