1 4 2 THE IN VOL UNTA R Y NER VO US S YS TEM 



according to my nomenclature, either connector or sensory fibres. 

 It is, however, very difficult to find any true nerve cells among 

 the mass of chromaffine cells which constitute the medullary 

 portion of the suprarenal ; certainly the number present is quite 

 insufficient to account for the number of splanchnic medullated 

 fibres which pass in. If we accept the embryological evidence 

 that these chromaffine cells are modified sympathetic nerve cells, 

 then the medullated fibres of the splanchnic are naturally the 

 connector fibres to these modified sympathetic nerve cells, and 

 the absence of a sufficient number of true ganglion cells is ac- 

 counted for. 



Smirnow in 1890 investigated the structure of the nerve 

 cells in the sympathetic of Amphibians, and found that, in 

 addition to true nerve cells, nests of peculiar cells were always 

 present in the sympathetic ganglia. He also found that the 

 nerve fibres going to and from these cell nests resemble in their 

 arrangement those going to and from the neighbouring nerve 

 cells so closely as to cause him to assert that these structures 

 are nests of sympathetic nerve cells, and he suggests that their 

 peculiarities may be accounted for on the supposition that they 

 are sympathetic cells in a young stage. He did not know of the 

 chromaffine cells at that time. Clearly these cell nests are the 

 chromaffine cells so universally found in the sympathetic ganglia 

 of Amphibians, and Smirnow's observations show that these cells 

 behave like sympathetic nerve cells in the arrangement of their 

 nerve fibres. 



Further there is some histological evidence which points in 

 the same direction. Macallum, at the meeting of the British 

 Association in Birmingham, showed that in sections of perfectly 

 fresh material, cut frozen and put into a solution of nitrate 

 of silver, all nerve cells took on a black staining, the most 

 intensive colour being in the cells of the sympathetic system. 

 No other tissues in the body were blackened except the medul- 

 lary cells of the suprarenal, which were stained as deeply as the 

 cells of the sympathetic ganglia. 



Again there is evidence that the action of sympathetic nerves 

 to the vascular musculature is dependent on a supply of 

 adrenaline. Elliott found that excision of the suprarenal glands 

 brought about the death of the animal in a short time, owing to 

 the great fall of blood pressure and marked weakness of the 



