94 WARFARE IN THE HUMAN BODY 



incomplete. So, too, with Phlogiston, which was both false 

 and true, and passed away as explanation when the actual 

 nature of combustion was discovered. Many such con- 

 ceptions must exist now, and possibly among them may be 

 reckoned some orthodox conceptions of physiology. 



It is a mark of false but useful theory that in the end 

 it raises more questions than it disposes of. In its 

 explanation other hypotheses are built up which contradict 

 each other, while none can be found to reconcile them. But 

 if the original conception is held obstinately, even further 

 observations are tortured into supporting it. In such 

 cases free speculation and criticism may play a useful part. 



If there is any physiological subject in which speculation 

 of all kinds is allowable on such grounds it is, perhaps, 

 Inhibition. There are facts of observation in abundance, as 

 any text-book of physiology proves, while the hypotheses, 

 sometimes misnamed theories, which seek to explain 

 them are both difficult and contradictory. It seemed to 

 me, when considering the subject, that the function of 

 the cardiac vagus, in which, according to accepted views, 

 inhibition means not only cessation of action in some 

 muscles, but the actual weakening of the whole heart, 

 might form a key, if not to unlock the mysteries of inhibition, 

 at the least to show some possible flaws in accepted opinion. 

 It appeared likely that not only had results obtained 

 in the laboratory, often of a pathological or traumatic 

 origin, not been compared with normal physiological action, 

 but that few inquirers had sought for analogies in other 

 organisms by which inhibition and its action could be 

 understood. It certainly appeared as if some clue were 

 needed to the problem, so far without real explanation, as 

 to the manner in which the vagus centre could "put the 

 heart out of action," and yet increase the action of the 



