152 VETERINARY PHYSIOLOGY 



(b) They may pass through these ganglia on to one more 

 peripherally situated in which they form synapses and are 

 continued onwards. These ganglia from which fibres do not 

 pass back are called collateral ganglia. Before their first 

 interruption they are termed pre-ganglionic fibres, after their 

 interruption post-ganglionic. 



The various fibres after their interruption proceed as non- 

 medullated or grey fibres to their termination, where they 

 join a network of anastomosing fibres with cells a sort of 

 terminal ganglion. Many drugs have a special action on the 

 terminal ganglia, e.g. apocodein paralyses them, while adrenalin 

 the extract of the medullary part of the suprarenals stimu- 

 lates certain of them. 



The interruption of fibres in ganglia, or their passage 

 through these structures, has been determined by taking 

 advantage of the fact that nicotine in one per cent, solution 

 when painted on a ganglion poisons the synapses but does not 

 influence the fibres. Hence, when a ganglion is painted with 

 nicotine, if stimulation of the fibres on its proximal side 

 produces an effect, it is proved that the break is not in that 

 ganglion. 



The arrangement of epieritic, protopathie and deep fibres 

 in the neuron and plexuses is considered at p. 170. 



Distribution 



A. SOMATIC FIBRES 



(a} Outgoing Fibres. The course of these must be studied 

 in the dissecting-rooin. 



(b) Ingoing Fibres. The fibres passing in by each pair of 

 nerves come from zones of skin encircling the body. These 

 are, however, interrupted by the limbs. Each limb may be 

 considered to be an outgrowth at right angles to the trunk, 

 composed of a pre-axial and post-axial part. 



B. SPLANCHNIC FIBRES 



(a) The Outgoing. Fibres may be divided into (fig. 76) 



A. The Thoracico-Abdominal Fibres, which come out in the 



