OF DEEAMS. 555 



and yet those animals sleep long and profoundly ; but if we reflect on 

 how many different conditions, external and internal, the repair of waste 

 depends, we shall see that the time of sleep can not have any such arbi- 

 trary measure as that of the size of the brain. Among external causes 

 which influence the rate of repair may be mentioned the digestibility of 

 the food, some varieties of which, by reason of their chemical or physi- 

 cal qualities, yield more slowly than others. The internal causes are very 

 numerous : the size of the digestive organs in relation to the Conditiong of 

 body, and the energy with which their function is accom- the duration of 

 plished ; the condition of development of the absorbent sys- s eep * 

 tern, and the rapidity of its action ; the rate of the circulation of the 

 blood, which hurries the nutritive supply in its course ; the amount of 

 oxygen introduced into the system by the respiratory apparatus, which 

 discharges, as we have elsewhere explained, the double function of re- 

 moving the wasted products of decay, and of grouping into appropriate 

 forms, so as to be available for their uses, the elements of nutrition that 

 are being introduced. All these, and other conditions that might be 

 named, determine the rate at which repair can be executed, and therefore 

 the necessary duration of sleep. If, out of these various elements, we 

 were to select one which would represent it, the activity of the respira- 

 tory organs would afford a more accurate measure than the size of the 

 brain. 



As the necessary repairs are accomplished, we pass through a condi- 

 tion of slumber, and our organs gradually awake in the manner that has 

 been described. It is during this intermediate passage, that is, toward 

 the morning chiefly, as the brain is resuming its functions, of dreams : 

 that dreams occur. They may, however, happen at any other their s> 

 period of the night, though then they are liable to present greater in- 

 congruities and more obvious violations of the proper order of events. 

 It is quite correct that morning dreams are more likely to be prophetic, 

 for they are more likely to be in themselves true. 



Dreams never strike us with surprise, no matter what may be the ex- 

 traordinary scenery they present no matter how great the violations of 

 truth and reality. The dead may appear with the most astonishing clear- 

 ness ; their voices, perhaps long forgotten, may be heard ; we may be 

 transported to places where we have spent past years of our lives ; com- 

 binations of the most grotesque and impossible kinds may be spread be- 

 fore us : we accept all as reality, perhaps not even suspecting that we 

 dream. The germs from which have originated all these strange com- 

 binations are impressions stored up in the registering ganglia of the brain, 

 more particularly in its optic thalami. These, as outward impressions 

 have for the time ceased, are enabled to attract the attention of the mind, 

 and emerge from their latent state. That all dreams originate in such 



