CRITICAL DIGEST. 



A DIGEST AND A CRITICISM OF THE DATA UPON WHICH 



IS BASED THE THEORY OF THE AMOEBOID 



MOVEMENTS OF THE NEURONE. 



By H. Heath Bawden. 

 I. Historical. 



The first researches which are significant in relation to the theory 

 of amoeboid movements of the neurone are those of His (45) which 

 show the migration of the neuroblasts from their primitive place of ori- 

 gin among the cells of the myelo-spongium to the point of exit of the 

 fibers of the anterior roots. ^ Here we seem to have an instance of true 

 amoeboid movement in the developing nerve cell. 



The next literature on the subject is an article by Rabl-Riickhard 

 (85) in the Neurologische Centralblatt for 1890 which relates to condi- 

 tions found in the case of the mature neurone. Without ostensibly de- 

 parting' from the generally accepted Gerlach conception, he simply 

 suggested the possibility of amoeboid changes in the network formed 

 by the protoplasmic processes of the neurones, coincident with different 

 functional states of the nervous tissue. In contrast with the current 

 view, which looked upon the elements of the nervous tissue as fixed in 

 form, this hypothesis possesses considerable significance. Rabl-Riick- 

 hard suggested the possible rupture of the filaments of the nervous 

 meshwork and their welding together again, employing the very ex- 

 pression " amoeboid movement " to describe this process in the proto- 

 plasmic branches of the neurones. His suggestion was, however, in 

 every sense an hypothesis, since there were at that time no researches 

 directly supporting such a view. 



About the same time there appeared an article by Wiedersheim 

 (109) in the Anatomische Anzeiger for 1890, on the brain of the tiny 

 transparent crustacean, Leptodora hyalina, with plates which showed 

 clearly certain changes of or within the nerve cells in that region of the 

 "brain" where it connects with the optic ganglion. These researches 



'Also from the spinal ganglia cells migrate to form the sympathetic system. 



