508 M. J. GREENMAN 



in numbers which, for each of these segments are equal to the 

 sum of the efferent fibers — taken in proportion to the weight of 

 the muscles — and of the efferent fibers — taken in proportion to 

 the area of the skin. 



Ingbert ('04) studied the areas of cross section in the ventral 

 and dorsal roots of the spinal nerves and computed the number 

 of sensory and motor fibers and showed that during the increase 

 in the nerve supply the gain has been more in the sensory than 

 the motor fibers. 



Donaldson and Hoke ('05) in a series of observations on the 

 spinal nerves of a number of vertebrates found that the relation 

 of axis cylinder to sheath was approximately as one to one. 



Boughton's ('06) results on the albino rat and on the cat cor- 

 respond with ours in finding an increase in the number of fibers 

 and an increase in size of fibers as the animal increases in weight. 

 He also points out that fibers which develop after the period of 

 rapid growth never attain large size. 



Perron cito ('06) showed that an axon begins to regenerate by 

 sprouting from the proximal stump within three hours after 

 section, and that in many cases a single fiber gives rise to many 

 sprouts. 



Osborne and Kilvington ('08) proved that bifurcation of motor 

 axons took place when a plurality of path was offered and that 

 motor axons would bifurcate and follow a sensory path as well 

 as a motor path. In a later paper ('09) they supplement their 

 results by further observations and state that bifurcation occurs 

 to some extent at the point of section as well as at the point 

 where plurality of paths is offered. 



Dunn ('09) in a paper on the albino rat observes the splitting 

 of nerve fibers and notes the deviation from the one to one 

 relation in the area of sheath and axis according to age. In a 

 later paper ('11) she observes the loss of fibers in old anunals. 



Ranson ('12) observed the branching of medullated nerve 

 fibers 5 mm. above the section. 



