REGULATORS 589 



either with or without its previous removal may be investi- 

 gated. 



This method has been largely used, but it must be employed 

 with great care for the following reasons : — 



i. The method of extraction may fail to remove the active 

 product from the structure. 



ii. The method of extraction may remove all sorts of con- 

 stituents of the structure, and any result produced may be due 

 to the combined action of many substances. 



iii. Products of decomposition may be removed either alone 

 or along with the active substance, and when administered may 

 produce symptoms which may be ascribed to an active con- 

 stituent which may not exist. The demonstration of the rapid 

 development in decomposition of amines having a powerful 

 physiological action shows that this is a real danger. 



iv. When massive doses of the extracts produce an effect, 

 there is a danger in concluding that a similar action is produced 

 by the amount normally poured into the blood, but it has been 

 shown that a massive dose may produce a totally different effect 

 from a small dose. 



V. It has been found that the action of these extracts may 

 be materially altered by the functional condition of the 

 structure to which they are applied; e.g. the uterus of the 

 virgin guinea-pig may respond quite differently from that 

 of the recently pregnant animal. 



vi. The method of administration may modify the action. 

 Thus, while the intravenous injection of the product of the 

 medulla suprarenalis causes very marked symptoms, these may 

 be entirely absent when it is injected under the skin or given 

 by the mouth. 



vii. Lastly, the danger of expectancy on the part of the 

 observer must not be overlooked. This is of no small import- 

 ance in the therapeutic administration of such extracts. 



Classification of the Endocrinetes — These endocrinetes are 

 derived from different parts of the embryo, and they may be 

 arranged according to their embryological source. Such a 

 classification is more satisfactory than one based upon their 

 anatomical position, for, in several cases, two of these organs, 

 entirely separate in origin, structure, and function, have come 



