ANATOMY, PHYSIOLOGY, OF NERVOUS SYSTEM. 451 



ment of this is schematically indicated in the accompanying 

 diagram, in which the reader will find it possible to follow 

 the description of the text. 



2 . The A rrangement of the 

 Sensory Neurons. The sensory 

 neurons are more complicated, 

 but in a general way here, too, 

 there are two neurons reaching 

 from the sense-organ to the 

 brain. The first neuron has its 

 cell body in the spinal root 

 ganglion. From this body one 

 nerve goes to the touch corpus- 

 cles, say of the finger, while 

 from the same body a second 

 nerve fiber runs into the poste- 

 rior horn of the spinal cord. 

 To repeat : One neuron bridges 

 the distance from the point of 

 touch in the finger to the spinal 



COrd with the Cell body of this Fig- 143 DIAGRAM TO SHOW PATHS OF 



NERVE-FIBERS IN THE SPINAL CORD. 



(After v. Lenhossek.) 



neuron located in the spinal 

 root ganglion. The endings of 



M, voluntary muscle; If, skin of 



., . -., ,, 1 1 hand; T, touch corpuscle; HW, posterior 



this sensory fiber m the cord root spinal nerve . VWt anterior root 

 are in a general way as follows: spinal nerve; pp > sensor y nerve '- # 



spinal root ganglion; s, cell body of sen- 

 As SOOn aS the fiber reaches sory neuron; m, motor cells in anterior 



the posterior horn it divides in- 



to an ascending and a descend- & lion ; . 6 a continuation of sensory 



. neuron c, upwards and downwards 



ing branch Which paSS Up and through gray matter of posterior horn; 



down respectively through the * * ne " r K on lying entirely within the 



cord, and by means of the collaterals a a, 

 gray matter of the posterior connecting opposite sides of the cord. 



horn. From these branches ^%SXS 



smaller branches called collat- P aths there described. 

 erals are given off at right angles. Some of these main 

 branches or collaterals may run into the anterior horns, and 

 there end in capillary dendrons which invest the motor cells 



