506 M. J. GREENMAN 



control, may be due to the branching which takes place in the 

 proximal zone when new fibers are produced at the expense of 

 the parent stem. 



In order to bring together the general results of the observa- 

 tions on the relations of the area of the axis and of the sheath, 

 figure 3 has been constructed. Jn this figure the total areas and 

 the axis sheath relations of the averages from the ten largest 

 fibers taken respectively from the normal, control and operated 

 nerves are given. In each instance the area of the fibers at the 

 proximal end, the middle zone and the distal end are drawn. 

 Where the determination depends on direct observation, the 

 medullary sheath is shown as a black ring, where the area has 

 been computed the outlines of both sheath and axis are indicated 

 by lines. The size of the fibers thus represented serves to show 

 more clearly, than the simple measurements can, the striking 

 modifications of the fibers which occur in the operated animals. 



LITERATURE 



The literature on the subject of regeneration has been care- 

 fully reviewed by Ranson (Jour. Comp. Neur., vol. 22, no. 6, 

 1912). We will, therefore, call attention only to those papers 

 dealing directly with the number of fibers (including branching), 

 their size and the axis-sheath relation in the peripheral nervous 

 system of vertebrates. 



Rudolph Wagner ('47) observed that in the distribution of 

 primitive fibers in the electric organ of fishes there is true branch- 

 ing and that one primitive fiber may have as many as twenty- 

 five branches. He demonstrated that the branching of nerve 

 fibers was a true branching and not the formation of a network. 



Schwalbe ('82) studied the size of fibers and the relation of 

 length to diameter. He attempted to show that the larger fibers 

 were distributed to the most distant parts. This was disproven 

 by Dunn ('02) in her study of the nerve fibers of the frog's leg. 

 Dunn here found a conical diminution in the nerve fiber in its 

 course. 



