Effects of Extirpation of the Salivary Glands. 39 



How can we conceive of inhibitive processes to explain a long 

 latent period of secretion, when chemical substances (for example, 

 salivary gland extracts) are injected intravenously ? By an anal- 

 ogous experimental reasoning, we have learned (Pawlow, /. c.) 

 that it is impossible to imitate the influence and action which the 

 vagus exerts during normal life while digestion is going on, for 

 our laboratory methods are far too coarse and the complexity of 

 fibers in this magnificent highway of nerve tracks too intricate 

 for us to single out individually functioning secretory fibers. 



We are not much better off when we attempt to imitate the 

 chemistry of the internal secretion of glands, for only in a single 

 instance has a hormon been isolated in a state that reveals its exact 

 chemic structure. 



The chemic messengers are bodies of definite chemic structure 

 which are released with unerring exactness from their producing 

 organs ; but when we manufacture an organ extract, it is, of course, 

 possible that we may seize the hormon (if I may still use the term) ; 

 but unavoidably we must extract the entire tissue of the organ and 

 as a result obtain extracts, which contain materials that stimulate, 

 but also materials that may inhibit secretion. This occasional 

 inhibitive effect of salivary gland extract on gastric secretion has 

 brought to mind two ideas : either that I am not dealing with a 

 hormon or stimulator at all, or that there may be two kinds of 

 chemic correlation, one that stimulates and the other that inhibits. 

 The conception which sees an antagonistic, as well as a syner- 

 gistic, correlation brought about by chemic messengers is at least 

 as rational, when applied to the physiologic correlation of organs 

 by means of chemic substances communicated to them by means 

 of the circulation, as when applied to the correlation of organs by 

 means of nerve elements. This relation of organs by means of 

 reciprocal (antagonistic or synergistic) action of nerves is not new 

 to physiologists, and has been brought home to us in a most im- 

 pressive manner by Meltzer, not to mention Ch. S. Sherrington, 

 New York, 1907. All of this is still hypothesis ; but this hy- 

 pothesis has been given color (i) by the seemingly paradoxical 

 effects of (a) such a pure substance as adrenalin, which does not 

 always cause constriction of vessels (only when they are severed 

 from the nerve centers) but sometimes may cause dilatation, when 

 in normal animals a certain vascular area is intact in connection 



