1892.] on the Physiology of Dreams. 597 



tins true wanderer runs, as you will observe, to the larynx, the 

 oesophagus, the heart, the stomach, conveying intelligence to the 

 brain of any local disturbance in those organs, and rousing up the 

 great nervous centres to exert themselves, and by a reflex notice to 

 the muscles, force the muscles to do their best to remove any 

 intruding cause of evil. 



We have not yet finished. If we follow those filaments of organic 

 nervous centres which are not our own and have nothing to do with 

 our royal wills, we find them accompanying the arteries which carry 

 the'vital blood to the extremest destination of the blood-serving or 

 arterial system, governing those vessels up to the minutest twig, and, as 

 the late Sir Thomas Watson simply but finely defined it, regulating 

 the supply of blood to every part, as a gas tap regulates flame, so 

 that the arterial vessels, in senseless pulsation during our lives, are 

 quickened, or slowed, by insensible direction, into various stages, from 

 the surface redness of rage to the pallor of death. 



In these mechanisms we see the origin of the subjective dream. 

 That indigestion, perturbation in the richly nerved digestive organs, 

 should lead to the transmission of vibrating and startling messages 

 to the mental centres, is simple truth enough ; that fever should 

 excite, and that every influence or disturbance — friction, distension, 

 heat — should disturb, in parts, the sensorium and conjure up a 

 phantasy, is no longer a mystery. It is a phenomenon that must be. 



Touching the efifect of external influences I have one word more to 

 add. Warmth of the air breathed by the sleeper favours dreams, 

 while coldness of the air disfavours them. Hence the vivid, brilliant 

 dream of the Asiatic, the dull dream of the Korthern blood. I have 

 been assured by one eminent Arctic explorer, the late Sir Edward 

 Belcher, that the Esquimaux do not know what dreaming means, and 

 our distinguished colleague Dr. Rae, in a letter I have before me, 

 says he does not recollect hearing of the phenomenon, although he 

 thinks such an imaginative people as the Esquimaux may dream. 



The reference to the effects of cold brings me to an experimental 

 demonstration bearing on motor and on sensory dreams. W^e all 

 know from our common experiences that there are in us two powers : 

 one of mind, the other of motion. If I were to enter fully into this 

 experience I might be able to prove tliat the two powers are essen- 

 tially one. It is enough now to explain, from what has preceded, 

 that in the dream the motor powers sleep, as a rule, uninterruptedly, 

 whilst the mental may be dreaming actively. We have, however, 

 seen exceptions to this rule ; and I may add that we can bring out 

 such exceptions by experiment. 



In some of my early experiments on the eJBfects of extreme cold on 

 nervous function, I found that the centres of nervous action could be 

 reduced to such inertia by cold that deepest sleep was inducible, 

 sleep leading to unconsciousness and perfect repose of all parts save 

 those which are under the influence of the organic nervous ganglia 

 and their fibres. Soon afterwards Dr. Weir Mitchell, of Philadelphia, 



