244 Journal of Comparative Neurology. 



were utilized later by Duval in support of the theory of amoeboid 

 movements. Observations of a similar nature had been made by two 

 other investigators, Svierczewski and Freud, but for some reason are 

 not referred to by Duval, though they are as conclusive as are those of 

 Wiedersheim. Svierczewski (105) in 1869 had made observations on 

 the cells of the frog's sympathetic ganglia kept alive in aqueous humor 

 or lymph, in which active changes were discovered within the nucleus. 

 The paper by Freud (37), which appeared in 1882, was on the living 

 ganglion cells of Astacus. He described little rods and angular shaped 

 shreds within the nucleus which in some instances changed their form 

 and position with astonishing rapidity. 



A paper by Tanzi (106) in the Re vista Sperimentale for 1893 

 touches on the subject and is quoted subsequently by Duval. Tanzi 

 calls attention to the growth changes which take place in the nerve cells, 

 particularly to the approximation of the cell branches. He suggested 

 that in the case of acts which by reason of habit or education take 

 place more or less easily and automatically the nervous current occa- 

 sioned a special nutritive activity, thus bringing about a hyper-nutrition 

 of the cells traversed by the nervous impulse. If, now, he says, this in- 

 crease in the volume of the nerve elements results, among other things, 

 in the elongation of the protoplasmic filaments, then the continued or 

 repeated passage of the nerve impulses within the limits of normal func- 

 tioning will gradually diminish the distance between the tips of the 

 contiguous branches of adjacent neurones. The actual functioning of 

 the nerve pathways, thus, would tend to increase the conductibility of 

 the chains of neurones for the nervous impulse. 



A Httle later, in 1894, Lepine (58) of Lyon, in connection with 

 certain observations on hysteria, set forth still other considerations as 

 to the possibility of variations in the relations of the neurones. He sug- 

 gested that a "psychical influence" might suffice to occasion that slight 

 displacement of the terminal ramifications necessary to obstruct the 

 passage of the nervous impulse, and that the reestablishment of this 

 connection takes place through a certain erethism of the cell resulting 

 in the approximation of the cell branches. It is not unreasonable to 

 suppose, he says, that sleep is occasioned by such relative isolation of 

 the neurones, and he thinks that the changes subsequent to this erethism 

 would explain the extraordinary suddenness with which we sometimes 

 pass from the sleeping to the waking state. 



The next year (Fel)rnary, 1895) appeared the first paper of Duval 

 (31) with the sub-tide " Theorie histologique du sommeil." Duval's 

 conception was apparently suggested by the fact, demonstrated by 



