Bawden, Movements of the Nejirone. 255 



elusions. Heger (44), also, arrives at similar results, though he finds 

 that the three types of variation in the fatigued cells, changes in the 

 cell body, in the dendrites, and in the geramules, do not necessarily go 

 together. Stefanowska's results (104), also, differ in no important re- 

 spect from those of Demoor. Manouelian (67) undertook to carry out 

 researches in which the facts dealt with should be more nearly normal 

 or physiological results than those of previous investigators. To this 

 end he brought about sleep through fatigue. He kept mice in a con- 

 stant state of excitement until they feel asleep from sheer exhaustion. 

 His results confirm those of the other investigators. Here, then, we have 

 the data upon which is built up the theory of the amoeboid movements 

 of the neurone. 



We pass to the criticism of the use of these data as evidence in 

 support of the theory of amoeboid movements. 



In the first place, it is to be noted that it is by no means univer- 

 sally agreed among histologists that the gemmules represent prolonga- 

 tions of the living cell. Serni-Meyer (99 and 100) denies their exist- 

 ence as genuine structures and explains them as due to the Golgi prep- 

 arations. Kolliker {^2) takes much the same view. 



The arguments for change in the position of the nucleus are more 

 or less ambiguous. Similar alterations in form and even extrusion of 

 the nucleus have been obtained in experimenting with the living 

 amoeba. How much of this effect is due to the action of the reagents 

 used remains to be determined. Hodge (48) has found similar con- 

 tractions of the nucleus in the living cell as the result of normal fatigue. 

 This shows that the observations above citf;d are certainly open more 

 or less to the interpretation of Duval and Ueyber. But as evidence 

 for the theory of amoeboid movement the facts are not clear because 

 of the lack of any criterion for what changes are due to the effect of 

 the reagent and what are the normal result of fatigue. 



No allowance is made in Duval's theory for the effects of the fix- 

 ating reagents. Attention maybe called to a paper by Professor Donald- 

 son in the Journal of Morphology (Vol. IX, No. i), entitled, " Prelim- 

 inary Observations on Some Changes Caused in the Nervous Tissues 

 by Reagents Commonly Employed to Harden Them." Professor Don- 

 aldson finds great changes in brain tissue under the influence of bichro- 

 mate of potash in which there is an increase of weight and volume, and 

 under the influence of alcohol in which there is a corresponding de- 

 crease in weight and volume.^ Similar observations have been made 



* This is but an example of the variations in volume caused by histological 

 reagents in general. 



