( 91 ) 



liealili, vvliilst sl(>e|)iii<i' oiilv tni- three or tuin- hours mit of llie 

 tweiity-fonr. Whetlier iii coming geiienitioiis sleep may hr (h'stincd 

 to vanisli altogetlier, cannot be predicted with ajiy certainty, because 

 we don't know the exact signiticance of sleep in the struggle for 

 life in its connection with the longer or shorter tei-ni of duration 

 of human life, and because on the other hand ^ve are not sui-e 

 whether some physiological process does not perliaps continue to 

 operate in the human organism, parallel with and dependent on the 

 alternating of day and night. 



The fact may be simply stated that man is the ojdy creatui-e 

 living upon the surface of the earth, capable of making himself no 

 longer dei)endent on the setting of the sun, by means of artificial 

 light, thus forcing the most intense stimuli to act without interrup- 

 tion on his nervous system. From the point of view of modern 

 science therefore the possibility cannot be excluded, that in some 

 remote future a race may exist, descended from man that will 

 have conquered the want of sleep, the term of dui*ation for iiidix i- 

 dual life, however, having become shortened. In this way the 

 knowledge of the primal cause of sleep in nature, f>pens a distant 

 prospect of the entire disappearance of sleep in man, who nevertheless, 

 because of reasons mentioned already, will never be able to pass 

 the first weeks of his life in a state of waking. 



Leiden, June 1903. 



Chemistry. — "The condition of h.i/dmtes of inckrlsidpliate in 

 methylalcoholic solution^ By Prof. C. A. Lobkv dk Bkuyn and 



C. L. JUNGIUS. 



1. It is known that tlic old question of the relation between a 

 dissolved substance and a solvent has been answered from two points 

 of view. Whilst particularly of late years, some have defended the 

 theory that the solvent is, as ir were, mci'ely a diluent which keeps 

 the dissolved molecules apart without entering into a closer relation 

 with them, others have upheld the view that the molecules of the 

 dissolved substance are most decidedly more or less sti'ongly united 

 to those of the solvent. Owijig to the development of the ionic theory, 

 the first assumption is now the more universal one particularly for 

 solutions of salts and their hydrates. On the other hand it must be 

 acknowledged that no strong evidence has ever been brought forward 

 to shovv the existence of hydrates of salts in an a(pieous solutioii 

 even though it seems natural to presume I hat to a certain extent 



