10 The Endocrine Organs 



at one time supposed, nor upon the presence of choline ; but seems to be caused 

 by an organic material of a specific nature which varies in different organs, the 

 extracts producing in each case a specific form of blood-pressure curve. 



Extracts of animal tissues — if unboiled — are liable to produce intravascular 

 clotting. If this is general, instant death is the result j if localised, it may manifest 

 itself by serious interference with the functions of the nervous system or of other 

 organs : and the result of such injection might erroneously be set down to a specific 

 action of the extract injected, although it would only represent the result of an 

 accident. A similar caution applies, although in a minor degree and for a different 

 reason, to effects which may be obtained as the result of buccal and hypodermic 

 administration of animal-extracts. Such effects may (unless they are otherwise 

 proved to be specific) be produced by variations in amount of such organic sub- 

 stances as nucleo-proteins, which, when added to the ordinary diet of animals, are 

 capable of affecting growth and metabolism. 



It is a perfectly legitimate criticism regarding the employment of 

 extracts of organs, that we are not justified in assuming that because 

 we obtain evidence of the presence of active substances in such extracts 

 they are necessarily preformed in the organ, and still less that they are 

 passed out from it into the blood. In fact, as we have seen, actual chemical 

 evidence of the presence of such substances in the circulatory fluids is 

 almost entirely lacking. Nevertheless, the action of extracts of certain of 

 the ductless glands is quite specific, which is not the case with extracts of 

 other organs ; and since the active principles contained in such extracts are 

 always readily soluble in water and diffusible, it is difficult not to believe 

 that they are formed with the object of producing their specific action after 

 being passed into the blood, in greater or less quantity according to the 

 needs of the organism. The criticism that with many such extracts an 

 amount of material may be necessary to produce a visible effect which is 

 altogether out of proportion to the size of the endocrine organ the action 

 of which is being studied, loses force if we remember that these organs 

 are extraordinarily vascular and probably proportionately active, so that 

 within a short time a larger amount of active substance may be formed and 

 passed into the blood than is present at any given moment in the cells of 

 the organ. Nor need the action, under physiological circumstances, be so 

 striking as we endeavour to obtain it under conditions of experiment ; 

 indeed it is not improbable that in many cases the functions of the internal 

 secretions under normal circumstances are rather facilitating than active. 



\\ The terms substitution therapy, organotherapy, opotherapy, and autotherapy are 

 employed to denote the effects produced by administration of organs and their 

 extracts — especially the endocrine organs — with the view to combat symptoms 

 which are believed to be caused by a deficiency in the blood of the autacoids 

 which are produced by those organs. The fact that such extracts have come 

 into extensive therapeutic use emphasises the essentially drug-like action of the 

 active substances they contain. Harrower {Practical Hormone Therapy) has col- 

 lected a large number of observations bearing upon this subject. 



