698 The Outline of Science 



ductless glands, and on the other the nervous system the brain 

 especially. The ductless glands are organs which pour their 

 secretions directly into the blood; and many of these secretions, 

 or hormones as they are often called, have an extraordinary 

 power over the growth of the body, its rate of working, and the 

 co-operation of its parts. The pituitary gland in the brain, for 

 instance, has a great influence upon growth, especially upon the 

 skeleton; giants usually seem to be produced by an excessive 

 development of this gland. The thyroid may be considered as 

 the draught of life's fire. If it is deficient, the fire burns low. 

 and there results a disease known as myxoedema, in which bodily 

 and mental processes are all sluggish. Too much thyroid, on the 

 other hand, leads to wasting away (in spite of increased appe- 

 tite), to increased pulse-rate, and to nervousness. Part of the 

 reproductive organs, the so-called interstitial tissue, also acts thus 

 as a gland, and produces a secretion which influences the growth 

 of all the bodily characters associated with one sex or the other, 

 and stimulates the brain, bringing into activity the sexual 

 instincts. 



Steinach in Vienna has found that rats which had begun to 

 show signs of senile decay could be rejuvenated by means of 

 operations which stimulated the interstitial gland, or by grafting 

 into them reproductive organs from young animals. As a result, 

 all the other ductless glands in the body were stimulated to 

 renewed life, and the failing brain and all its mental faculties 

 were revivified. By this means, he was able to prolong the life 

 of rats by about 40 per cent. These results so far stand alone; 

 they need confirmation on other animals, and long testing to see 

 whether they are applicable to man; but at least they open a 

 window on to new fields of work, and show what revolutionary 

 results may be expected when biological research finds men, 

 money, and time (for it is a laborious, expensive, and delicate 

 business!) to investigate in fullness of detail the complicated 

 machinery of the mammalian body. 



