592 



THE NEEVOUS SYSTEM 



glia along the fibers of the vagus nerves. Kuntz believes that 'indirect 

 embryological and anatomical evidence warrants the conclusion that the 

 sympathetic excitatory neurons arise from cells which migrate from the 

 neural tube along fibers of the motor nerve roots, while the sympathetic 

 sensory neurons, wherever such neurons exist, arise from cells which 



migrate from the cerebrospinal 

 ganglia/ However, according 

 to Carpenter (1914) the autono- 

 mic neurons show no distinct 

 differences from the standpoint 

 of their chromophilic content. 

 Since such differences are con- 

 spicuous between the sensory 

 and motor neurons of the cere- 

 brospinal system (Malone), this 

 observation arouses skepticism 

 regarding the presence of sen- 

 sory sympathetic ganglion cells. 

 The primary cerebral divi- 

 sions (Fig. 516) and their ma- 

 jor adult derivatives are enu- 

 merated in the appended out- 

 line. The microscopic anat- 

 omy of their definitive condi- 

 tion lies outside the scope of 

 this book. These matters are 

 more appropriately treated in 

 special text-books of Neurology 

 (e.g., Quain's "Anatomy," Vol. 

 Ill, 1908; and Villiger's "Brain 

 and Spinal Cord," translation 



FIG. 514. TRANSECTION OF THE SPINAL 

 CORD OF A HUMAN EMBRYO OF FOUR 

 WEEKS. 



The central canal is immediately sur- 

 rounded by ependyma cells. The peripheral 

 nerve cells are shown on the left of the figure. 

 The ventral nerve roots are already pushing 

 outward from the primitive cord, d, dorsal; 



v, ventral nerve roots. (After His.) by Piersol, 1912) and constitute 



the work of a separate course. 



Likewise the developmental history is more advantageously considered in a 

 special course in Embryology. 



This work will include only the histology of sections of the spinal 

 cord; and that of the cerebellar and cerebral cortex. 



