278 TRANSACTIONS OF SECTION H, 



Professor Glynn ' has recently collected such cases and systematised our know, 

 ledge of these strange derangements of growth. There can be no doubt that 

 the suprarenal bodies constitute an important part of the mechanism which 

 regulates the development and growth of the human body and helps in deter- 

 mining the racial characters of mankind. We know that certain races come 

 more quickly to sexual maturity than others, and that races vary in development 

 of hair and of pigment, and it is therefore reasonable to expect a satisfactory 

 explanation of these chai-acters when we have come by a more complete knowledge 

 of the suprarenal mechanism. 



During the last few years the totally unexpected discovery has been sprung 

 upon us that disease of the minute pineal gland of the brain may give rise to a 

 train of symptoms vei-y similar to those which follow tumour formation of the 

 cortex of the suprarenal bodies. In some instances the sudden sexual pre- 

 maturity which occurs in childhood is apparently the immediate result of a 

 tumour-like affection of the pineal gland. We have hitherto regarded the 

 pineal gland, little bigger than a wheat-grain and buried deeply in the brain, 

 as a mere useless vestige of a median or parietal eye, derived from some distant 

 human ancestor in whom that eye was functional, but on the clinical and 

 experimental evidence now rapidly accimiulating we must assign to it a place 

 in the machinery which controls the growth of the body. 



We come now to deal with the thyroid gland, which, from an anthropological 

 point of view, must be regarded as the most important of all the organs or 

 glands of internal secretion. Here, too, in connection with tJie thyroid gland, 

 which is situated in the front of the neck, where it is so apt to become enlarged 

 and prominent in women — I must call attention to a generalisation which I 

 slurred over, when speaking of the pituitary and suprarenal glands. Each of 

 these glands throws into tlie circulating blood two sets of substances — one set 

 to act immediately in tuning the parts of the body which are not under the 

 influence of the will, to the work they have to do when the body is at rest 

 and when it is making an effort; another set of substances — which Prof. Gley 

 has named morphogenetic — has not an immediate but a remote effect ; they regu- 

 late the development and co-ordinate the growth of the various parts of the 

 body. Now, so far as the immediate function of the thyroid is concerned, 

 our present knowledge points to the gland as the manufa<;tory of a substance 

 which, when circulating in the body, regulates tlie rate of combustion of the 

 tissues ; when we make a muscular effort, or when our bodies are exposed to 

 cold, or when we become the subjects of infection, the thyix>id is called upon 

 to assist in mobilising all available tissue-fuel. If we consider only its immediate 

 function it is clear that the thyroid is connected with the selection and survival 

 of human races. When, however, we consider its remote or morphogenetic I 

 effects on growth its importance as a factor in shaping the characteristics of I 

 human races becomes even more evident. In districts where the thyroid is! 

 liable to that form of disease known as goitre it has been known for many 

 a year that children who were affected became cretins — dwarf idiots with a 

 very characteristic appearance of face and body.- Disease of the thyroid stunts 

 and alters the growth of the body so that the subjects of this disorder might 

 well be classed as a separate species of humanity. If the thyroid becomes 

 diseased and defective after growth of the body is completed then certain 

 changes, first observed by Sir WMliam Gull in 1873, are set up and give rise to 

 the disordered state of the body known as myxoedema. ' In this state.' says 

 Sir Malcolm Morris, ^ ' the skin is cold, dry and rough, seldom or never perspires, 

 and may take on a yellowish tint ; there is a bright red flush in the malar region. 

 The skin as a whole looks transparent ; the hair of the scalp becomes scanty ; 

 the pubic and axillary hair, with the eyelashes and eyebrows, often falls 

 out; in many cases the teeth are brittle and carious. All these appearances 

 disappear under the administration of thyroid extract.' We have here con- 

 clusive evidence that the thjToid acts directly on the skin and hair, just the 

 structures w'e employ in the classification of human races. The influence of 



' Quart. Journ. of Med., 1'912, vol. v., p. 157. 



- The story of the discovery of the action of the thvroid gland is told 

 by Prof. G. M. Murray, Brit. Med. Journ., 1913, II.. p. 163. * 

 " Brit. Med. Journ., 1913, I., p. 1038. 



