NERVOUS SYSTEM 



107 



the area of the axones of the ventral root fibers increases with 

 the increase in the mass of muscle innervated (loc. cit). 



Axis sheath relation. In the case of the fibers in the ventral 

 spinal roots, the dorsal roots and the seventh nerve, the per- 

 centage area of the axis, determined by the method of diameters, 

 is shown in table 69. In all three localities the values are similar. 

 They increase slightly after 24 days of age but after puberty 

 approximate 50 per cent. These results agree with those pre- 

 viously obtained by Dunn ('12) when the relations at like ages 

 are compared. 



TABLE 69 



Giving the areas of nerve fibers and their axes in square micra- — also the percentage 

 of the total area occupied by the axis, based on groups of three 



Sympathetic. In the course of a study intended primarily 

 to determine whether the small myelinated fibers in the spinal 

 accessory could be regarded as representing the fibers of the 

 rami communicantes, Roth ('05) in a series of cervical nerves, 

 counted on one side the number of myelinated fibers 4 /x or less 

 in diameter, and in the corresponding ramus communicans he 

 also counted the myelinated fibers of like size. His findings 

 are given in table 70. 



In the standard strain of the albino rat from The Institute 

 the cell bodies in the superior cervical sympathetic ganglion 

 grow rapidly for the first twenty-five days after birth — then 

 more slowly. After puberty the cells are slightly larger in the 

 female (Ping, '21)— table 71. 



