iso VP:TERINARY PHYSIOLOGY 



body wall and its appendages and those connected with the 

 viscera. 



A dorsal root (PM.) comes off from the dorso-lateral 

 aspect of the cord and has a swelling upon it, the ganglion 

 of the dorsal root. It joins a ventral root (AM.) coming 

 from the ventro-lateral margin. These form the spinal nerve 

 which is distributed to the body wall. Lying in front of "this 

 is a swelling or ganglion (S.I.) joined to the nerve by two roots, 

 a white ramus ( W.R). and a grey ramus (G.R.) ; and from this 

 a nerve extends towards the viscera ( V.N.). Before this nerve 

 reaches its final distribution it passes through another ganglion. 



Roots of the Spinal Nerves. The dorsal root is the great 

 ingoing channel to the spinal cord, and the ventral root is 

 the great outgoing channel. Section of a series of dorsal 

 roots leads to (a) loss of sensation in the structures from 

 which the fibres come, and (6) to a loss of muscular co-ordina- 

 tion, as a result of cutting off the afferent impressions con- 

 nected with the kinaesthetic sense (p. 102). 



As a result of this section, the parts of the fibres cut off 

 from the cells of the ganglia on the dorsal root die and 

 degenerate (see p. 85). Therefore, if the root is cut inside 

 the ganglion, the degeneration extends inwards and up the 

 dorsal columns of the cord, and if it is cut outside, the 

 degeneration passes outwards to the periphery. 



Section of the ventral root causes paralysis of the muscles 

 and other structures supplied by the outgoing fibres, and the 

 fibres die and degenerate. 



The nerve to the somatopleur or body wall (S.N.) is composed 

 of incoming and outgoing fibres. 1st. Incoming fibres are 

 medullated and take origin in the various peripheral sense 

 organs. As they pass through the ganglion on the dorsal 

 root each fibre is connected by a side branch with a nerve cell 

 the trophic centre of the neuron and it then enters the 

 spinal cord, and either passes to the dorso-lateral column, or 

 forms synapses in the cord (see p. 87). 2nd. Outgoing fibres 

 are medullated, and take origin from the large cells in the 

 ventral horn of the grey matter of the cord and pass on to 

 be connected with muscle fibres by end plates or to gland cells 

 by less definite synapses. 



The nerve to the viscera or splanehnopleur (V.N.), and to 



