December i, 1923] 



NA TURE 



797 



condition of ignorance extends to most of the other 

 ductless glands. 



In some cases deficient production of a hormone 

 may be due to the absence from the food and drink 

 of some necessary constituent. Thus iodine is essential 

 to the formation of the specific secretion of the thyroid 

 gland (iodothyrin). If iodine be entirely absent from 

 the drinking water and the soil, so that it is not con- 

 tained even in minute quantities in the vegetable 

 food grown in the district, the thyroid undergoes 

 hyperplasia — in vain an endeavour to make bricks 

 without straw, to produce its proper hormone without 

 iodine. This seems to be the cause of the great pre- 

 valence of simple goitre in certain districts — especially 

 in Switzerland and in parts of the United States. 

 It has been shown that goitre can be practically 

 eliminated from these districts by the occasional 

 administration of small doses of iodine or iodides 

 (Marine, Lenhart, KimbuU, and Rogoff). These results 

 were communicated in 191 7 to Dr. Klinger of Ziirich, 

 and as a result of his experience the Swiss Goitre 

 Commission has recommended the adoption of this 

 method of goitre prevention as a public health measure 

 throughout the entire State. Already great progress 

 has been made in the abolition of this disease from 

 the country. Thus the incidence of goitre among 

 all the school children of the canton of St. Gallen has 

 been reduced from 8y6 per cent, in January 1919, 

 to i3'i per cent, in January 1922. 



(2) Where a disordered condition is due to diminished 

 production of some specific hormone we may extract 

 the hormone from the corresponding gland or tissue 

 in animals. It is characteristic of these hormones 

 that, so far as we know, they are identical throughout 

 all the classes of vertebrates, and it is possible that 

 they may be found far back in the invertebrate world. 

 This method is easy when, as in the case of the thyroid, 

 the active principle is stored up in the gland and is 

 unaltered by the processes of digestion, so that we 

 can obtain all the curative effects of the hormone 

 if we administer dried thyroid by the mouth. We 

 have no evidence that any other of the hormones 

 with which we are acquainted partake of this resistance 

 to digestion, so that to produce their specific effects 

 they have to be introduced by subcutaneous injection 

 — a great drawback when the administration has to 

 provide for the constant presence of a small con- 

 centration of the hormone in the blood and tissues. 

 In the case of insulin, for example, it seems necessary 

 to repeat the injection every twelve hours to obtain 

 any continuity of action, and the same thing probably 

 applies to the pituitary extract, while in the case of 

 the genital hormones no trustworthy effect has been 

 obtained except by the actual implantation of the 

 organ from an animal of the same family.^ 



• In ray Croonian Lectures in 1905 I reported some experiments made 

 in conjunction with Dr. Lane-Claypon, in which I had produced hyper- 

 trophy o( the mammary glands in virgin rabbits, and in some cases actual 

 secretion of milk, by the daily subcutaneous injection of the filtered watery 

 extract of yn.mk' r:\hbit frrtu^cs. Similar results were obt-iincd by FoJi. 

 But .1 ' ■ liments was that the ovaries had not been 



previa :i.| Bouin have shown that in the rabbit 



the III. ; i)f a Graafian follicle, with the subsequent 



growth lit .1 .(iipiis luicuiii, arc sufficient to cause hypertrophy of the 

 mammary glands (the effective hormone presumably having its scat of 

 manufacture in the luteal cells). It seems possible, therefore, that the 

 eflect of our injortions may have been on the ovaries, and that the growth of 

 the mammary glands was only a secondary and indirect result. I do not 

 therefore now regard our experiments .is conclusive. 



NO. 2822, VOL. I 12] 



We may, however, look forward to the day when 

 the chemical constitution of all these hormones will 

 be known, and when it may be possible to synthesise 

 them in any desired quantity. We may then be able 

 to overcome the inconvenience of subcutaneous in- 

 jection by giving relatively colossal doses by the mouth, 

 or we may be able to modify their constitution to a 

 slight extent so as to render them immune to the 

 action of digesting fluids, without affecting their 

 specific action on the functions of the body. 



(3) The ideal, but not, I venture to assert, the un- 

 attainable, method will be to control, by promotion or 

 suppression, the growth of those cells, the function of 

 which is to form these specific hormones. Though 

 this method seems at present far from realisation, 

 the first steps in this direction have already been taken. 

 It must be remembered that the power of controlling 

 growth of cells involves the solution of the problem 

 of cancer. Here the experiments on the growth of 

 normal cells outside the body have shown that they 

 can be stimulated to vie with cancer cells in the rate 

 of their growth, or can be inhibited altogether accord- 

 ing to the nature of the chemical substances with 

 which they are supplied. We know that the growth 

 of certain cells, such as those of the mammary gland 

 or of the uterus, is excited by specific chemical sub- 

 stances produced in the ovary or foetus ; and we may 

 be able to find specific substances or conditions for 

 any tissue of the body which may excite growth 

 which is retarded, or diminish growth when this is 

 in excess. 



It may be that in some cases purely mechanical 

 interference will suffice. Thus in experiments by 

 Steinach and others it has been found that ligature 

 of the vas deferens close to the testis, while causing 

 atrophy of the seminiferous cells, brings about over- 

 growth of the interstitial cells, which, as we have seen, 

 are chiefly responsible for the hormones determining 

 the secondary sexual characters. Among these second- 

 ary sexual characters must be classed the whole of a 

 man's energies. Virility does not mean simply the 

 power of propagation, but connotes the whole part 

 played by a man in his work within the community. 

 As a result of this hypertrophy these authors claim 

 to have produced an actual rejuvenation in man, 

 and thus to have warded off for a time senility with 

 its mental and corporeal manifestations. Further 

 experiments and a longer period of observation are 

 necessary before we can accept these results without 

 reserve, but it must be owned that they are perfectly 

 reasonable and follow, as a logical sequence, many 

 years' observations and experiments in this field. 



It would indeed be an advantage if we could post- 

 pone the slowly increasing incapacity which affects 

 us all after a certain age has been passed. Pleasant 

 as it would be to ourselves, it would be still more 

 valuable to an old community such as ours, where 

 the arrival of men in places of rule and responsibility 

 coincides frequently with the epoch at which their powers 

 are beginning to decline. The ideal condition would 

 be one in which the senile changes affected all parts 

 of the body simultaneously, so that the individual 

 died apparently in the height of his powers. For it 

 must not be thought that in any such way we could 

 prolong life indefinitely. Pearl has pointed out that 



