204 OF SLEEP. 



the renewal of the stimulus. The case of the brain is analogous ; 

 and when, after its daily activity, it falls asleep, the diminution 

 of its circulation consequentiy ensues. 



(C) In sleep the action of the mind is considerably sus- 

 pended. But the degree of suspension is extremely various. In 

 ordinary sleep the mind is sufficiently alert to feel unpleasant 

 sensations and make an effort to remove their causes ; whether 

 to remove the uneasiness of impeded circulation in the lungs by 

 breathing, or to draw away the hand when tickled. Imagination 

 is often active, and one idea associates with it another, consti- 

 tuting dreaming ; but the activity of the mind is partial, and 

 though we are able occasionally even to reason correctly in our 

 dreams, we are not sufficiently ourselves to discover the incom- 

 patibility of many circumstances which we fancy. In a higher 

 degree of activity, we answer questions put to us, although often 

 ridiculously, as our deficiency of mental power prevents us from 

 keeping our associations in a proper train ; and we sometimes 

 even perform a regular series of movements. 



The great feature of sleep is the deficiency of our active 

 powers. If we have any external sensation, or if the imagination 

 riots on, presenting trains of images to our internal senses, we 

 reflect upon them but weakly, make great mistakes, and however 

 well we may reason, or whatever corporeal movement we execute, 

 the inferiority of our active powers is conspicuous. But that 

 active power is not suspended, as Mr. Dugald Stewart maintains 

 in his theory of dreaming,* the simple fact of breathing during 

 sleep, to say nothing of the other motions, and the acute, though 

 circumscribed, reasoning Avhich occasionally occurs, is a suffi- 

 cient proof. 



* Elements of the Philosophy of the Human Mind. Vol. 1. 



