HISTORY OF THE INVOLUNTARY NERVOUS SYSTEM 15 



These conclusions as to the relation of the sympathetic nerve 

 cells to the fibres of the white rami communicantes were confirmed 

 by Langley and Dickinson in 1889 in consequence of observations 

 upon the action of nicotine ; for they showed that the injection of 

 nicotine prevented the effect of stimulation of the fibres from the 

 spinal cord which go to the sympathetic ganglia, i.e. the ramus 

 communicans, but did not affect the fibres from the sympathetic 

 ganglia. In other words, the action of the nicotine upon the 

 sympathetic cell or upon the junction of the spinal fibre and 

 the sympathetic cell prevented the action of the latter fibres. 



These spinal fibres Langley named " pre-ganglionic," and the 

 sympathetic fibres " post-ganglionic ". 



There are two distinct groups of ganglia belonging to this 

 system, in the first place a chain of ganglia lying along the 

 vertebrae on each side, the vertebral or lateral ganglionic chain, 

 and in the second place, ganglionic masses lying on each side 

 of the abdominal aorta which form the prevertebral or collateral 

 ganglia. These latter form two principal groups of ganglia, the 

 largest and most anterior forming a mass round the coeliac axis 

 which is often called the solar ganglion. 



This mass is divisible into two parts, the semilunar ganglia 

 and the superior mesenteric ganglia. The sympathetic fibres aris- 

 ing from the cells of the semilunar ganglia pass with the blood 

 vessels to the stomach, liver and spleen, and those from the cells 

 of the superior mesenteric ganglia run with the branches of the 

 superior mesenteric artery, and are therefore concerned with the 

 innervation of the small intestine and its blood vessels. In 

 addition to the superior mesenteric and semilunar ganglia there 

 is also a small ganglion found on each side, the renal ganglion, 

 which supplies the kidney with sympathetic fibres. 



The smaller posterior group forms a ganglionic mass which 

 bears the same relation to the inferior mesenteric artery as the 

 larger mass does to the superior mesenteric, and its sympathetic 

 fibres pass to the periphery with the branches of the inferior 

 mesenteric artery ; they are concerned with the innervation of the 

 large intestine and its blood vessels. 



Between the inferior and superior mesenteric ganglia a small 

 ganglion is found on the walls of the aorta the ovarian or sper- 

 matic ganglion the fibres from which pass to the ovaries or 

 testis by way of the ovarian or spermatic artery respectively. 



