1 4 THE INVOL UNTAR Y NER VO US S YSTEM 



medullated fibres were not uniformly present. They were most 

 prominent in the second and following thoracic roots, and were 

 found in the anterior roots throughout the whole thoracic region 

 and the beginning of the lumbar region. I found, as naturally 

 was to be expected, that they corresponded to the region of white 

 rami communicantes ; above and below this region there are only 

 grey rami communicantes ; the white are absent. This peculiar- 

 ity of the anterior roots in the thoracic region had been noticed 

 by Reissner, but he could not explain it. 



These observations showed that the central nervous system 

 supplies efferent fibres in the white rami communicantes to the 

 main sympathetic chain only in the thoracico-lumbar region. 



The next question was to find out the relation between the 

 fine white medullated cerebro-spinal fibres and the grey non-medul- 

 lated sympathetic fibres. I argued as follows : the accelerator 

 nerves to the heart from the ganglion stellatum and inferior 

 cervical ganglion are clearly non-medullated ; stimulation of the 

 second and third roots in the thoracic region cause acceleration ; 

 these accelerator fibres pass to the ganglion stellatum along 

 the rami communicantes and are medullated right up to the 

 ganglion ; the conclusion is that the medullated fibres, which 

 cause acceleration, end in sympathetic cells in the ganglion, and 

 that these cells give origin to the non-medullated accelerator fibres 

 which pass to the heart. I argued similarly with respect to the 

 whole group of vaso-constrictor nerves, which also leave the 

 spinal cord as fine medullated nerves and pass to the blood 

 vessels from sympathetic cells as non-medullated fibres. The 

 conclusion then to which I came in 1885 was that the sympathetic 

 cells consisted largely, if not entirely, of a system of motor cells 

 situated on the path of efferent fibres from the cord to the 

 peripheral organ ; that in fact both roots might be looked upon 

 as ganglionated, the anterior as well as the posterior. With the 

 coming in of the neuron theory, and the conception of a series 

 of relays in the nervous system, it is held that these motor cells 

 represent the terminal neurons of the efferent system, just as the 

 sensory cells of the posterior root ganglia represent the terminal 

 neurons of the afferent system ; the difference between the two 

 sets being the fixed position of the latter on the posterior roots 

 just near the spinal cord, and the vagrant character of the former 

 at various distances from the cord. 



