Meyer, Data of Modem Neurology. 139 



The median line on the ventral side is usually called rapJie ; 

 the portion next to it, the ventral or basal lamina of the tube, 

 develops the motor neurones, the cells which send their fibers 

 into the muscles, and cells of an intersegmental character, the 

 processes of which do not leave the neural tube but grow in a 

 longitudinal course into other segments (ground-bundle-cells). 

 The dorso-lateral part of the tube-wall ( also called wing-plate ) 

 receives the central termination of the afferent neurones, the 

 cells of which are located in the ganglia outside. This dorso- 

 lateral part, or posterior horn, contains cells which belong to 

 the order of intermediate cells or shunt-cells. We shall see 

 later on, how these intermediate cells become more specialized. 

 Looking at an entire row of segments of the neural tube, 

 we find the following general arrangement : a small point of the 

 skin is connected by an afferent nerve-element with the corres- 

 ponding segment of the neural tube (spinal cord or brain-stem). 

 One process of the cell reaches the skin ; the other process 

 grows as a fiber of the posterior root into the dorsal part of the 

 neural tube. Directly after entering, it divides into a branch 

 which runs towards the head and one which runs towards the 

 caudal segments. Each branch gives off collaterals which 

 terminate in various parts of each segment : some of them in 

 the dorso-lateral plate, ending among shunt-cells, others in the 

 ventral or motor plate, among the motor neurones. As in the 

 worm, we see o)ie afferent neurone reacJdng many motor cells and 

 many shnnt-cells. This is of great importance as is readily 

 seen from this consideration : Each motor neurone is con- 

 nected with certain definite muscle-fibrils on which it ends as 

 end-plate. If these muscle-fibrils belong to a flexor muscle, 

 the neurone might be called flexor-neurone, if the muscle is an 

 extensor or rotator or abductor or adductor, the neurones be- 

 longing to each respectively are extensor, rotator, abductor, or 

 adductor neurones. Now it is very probable that a sensory 

 neurone supplying the volar side of a thumb gets into contact 

 with sets of motor neurones connected with the various groups 

 of muscles of the thumb. You might suppose that, if this 

 were really the case, a stimulation of any part would call forth 



