vj, SYMPATHETIC SYSTEM 369 



names of pre-cellular and post-cellular fibres, or called them viscero- 

 motor fibres of the first and second order. Langley objected that 

 " a pre-ganglionic fibre is post-cellular, in relation to the nerve- 

 cell from which it arises " ; while the second term is too limited, 

 as it does not include the secretory fibres. We therefore adopt 

 Langley's nomenclature. 



The nicotine method is not conclusive since the action of 

 nicotine differs in different cases. In certain animals, as the dog, 

 it has hardly any effect ; in different animals of the same species, 

 again, or in different sympathetic regions in the same animal, it 

 acts differently. The splanchnic system, for instance, is more 

 resistent to its action than the cervical sympathetic. The paralytic 

 phenomena are usually preceded by phenomena of excitation. In 

 birds nicotine excites and causes erection of the feathers without 

 paralysing the ganglia. 



The results of the nicotine methods were substantially confirmed 

 by Langendorff (1891-92), who saw that in the period immediately 

 preceding the animal's death stimulation of the fibres that run to 

 the superior cervical ganglion and the ciliary ganglion fails to 

 produce any effect long before the nerves that emerge from these 

 ganglia become inexcitable. 



To sum up, we may conclude that the efferent sympathetic 

 fibres issuing from the cord never like the motor fibres to the 

 skeletal muscles run uninterruptedly to the organs innervated ; 

 they terminate, after a longer or shorter course, in a ganglion. 

 Some end in the first ganglion they encounter; others, on the 

 contrary, pass through several ganglia before reaching their 

 terminal station on their way they may send collaterals to a 

 great number of different cells. There is only one break in the 

 efferent sympathetic path, since the post-ganglionic fibres, according 

 to Langley, always run without further interruption to the peri- 

 pheral organs which they supply. 



The great majority of the post-ganglionic fibres from the 

 ganglia of the lateral chain run back in the grey rami to the 

 corresponding spinal nerves, or to the next higher or lower spinal 

 nerve, to innervate the peripheral organs served by the sympathetic, 

 in the regions to which these spinal nerves are distributed (skin 

 system). Where the spinal nerves innervate segmentally distinct 

 regions, for instance in the trunk and neck, the skin fields 

 supplied by the grey rami do not overlap at all, or only by about 

 1-2 mm. But in regions in which the spinal nerves form plexuses, 

 the areas innervated by the various grey rami do overlap to a large 

 extent, as can readily be demonstrated by producing sweat 

 secretion of a cat's pad by stimulating the grey rami of different 

 spinal nerves. 



According to Langley, the stellate and the superior cervical 

 ganglion not only give off post-ganglionic fibres to the corre- 



VOL. in 2 B 



