534 Mr. Walter H. Gaskell [June 4, 



I know no other bundle of nerve-fibres wliicTi is so absolutely free 

 from meduUated nerves : in other words, nerve-fibres of the same 

 function enter a sympathetic ganglion as white medullated fibres 

 and leave it in increased numbers as grey non-meduUated nerves. 



Throughout we find the same fact, all the vasomotor nerves behave 

 in exactly the same manner as the accelerators of the heart. In all 

 cases the non-medullated fibres of the sympathetic are simply the fine 

 medullated visceral nerves which have passed from the spinal cord in 

 one or other of the three visceral outflows and lost their medullary 

 Bheath in their passage through the ganglia of the sympathetic system ; 

 together with that loss of medulla they have increased in number by 

 division. 



Seeing then that the non-medullated (so-called sympathetic) 

 nerve-fibres are throughout modified medullated (so-called cerebro- 

 spinal) fibres, and do not, therefore, arise in the sympathetic ganglia, 

 we may fairly look upon the sympathetic ganglia as bearing the same 

 kind of relation to the visceral nerves that the ganglia of the posterior 

 roots bear to the ordinary sensory nerves. This conception is re- 

 markably confirmed by the observations of Onodi, who has shown that 

 the ganglia of the sympathetic are developed in close connection with 

 the posterior root ganglia, and travel further away from the central 

 axis as the animal grows. 



Finally, the meaning of the sympathetic as a simple outflow of 

 ganglionated visceral nerves from certain portions of the spinal cord 

 and medulla oblongata is to my mind conclusively settled by the 

 intimate relationship which exists between the structure of the spinal 

 cord and the presence or absence of rami viscerales. In the grey 

 matter of the spinal cord we find, as shown in the accompanying dia- 

 gram, certain well-defined groups of nerve-cells, viz. a, a group of 

 large nerve-cells in the anterior horn (4 in Fig.) ; these are known to 

 be the origin of ordinary motor-fibres (4) ; h, a group of nerve-cells 

 (3) split off from this and forming the lateral horn ; c, a group (2) 

 known as Clarke's column; and d and e, two sets of nerve-cells 

 (4 and 5) in the posterior horn connected with sensory nerves. All 

 these groups of nerve-cells are found along the whole length of the 

 spinal cord, except those of Clarke's column. Their connection with 

 nerve-fibres of different functions is known, except those of Clarke's 

 column. Thus both sets in the anterior horn are connected with 

 ordinary motor nerves ; both sets in the posterior horn with ordinary 

 sensory nerves. Now Clarke's column is limited to certain definite 

 regions of the cord, being conspicuous : firstly, between the second 

 thoracic and second lumbar nerves ; secondly, at the top of the cervical 

 region and extending into the cranial region ; and thirdly, an isolated 

 patch in the sacral region. In other words, its cells correspond 

 exactly in position to the distribution of tlie white rami communi- 

 cantes, so that, corresponding to the variation of this cell-group we 

 find variations of the number of very fine medullated fibres in the 

 anterior roots, and we find corresponding variations in the white rami 



