76 SCIENCE PROGRESS. 



not true reflexes, as they occur in the grey matter of the cord, 

 but are probably due to the stimulus running up an efferent 

 fibre and down a collateral of that same fibre and so brinQ^inQ^ 

 about the muscular contraction. Another view of the part 

 played by the cells is that through them the fibre loses its 

 medulla and becomes non-medullated ; but this we have 

 seen is not general. There is a final suggestion that a few 

 nerve fibres run to these cells, and that many more fibres 

 run from them. That, in a way then, there is a multiplica- 

 tion of fibres as they travel through the ganglion, a point 

 which will require only a few fibres to run from the cord 

 and yet readily allow of a wide peripheral distribution. 

 This is of course an obvious advantage where a large 

 peripheral area is always required to work as a whole and 

 in the same sense. 



The general arrangement of the nerve cells anatomically 

 as contrasted physiologically also shows some uniformity, 

 and allows us to draw conclusions with respect to the 

 morphological inter-relationships of the various ganglia. 

 Thus, in the lateral chain of ganglia we find the cells on the 

 course of the pilo-motor nerves, splenic nerves, and some 

 vaso-constrictors {to surface of trunk). In the collateral 

 chain are found the cells of many vaso-constrictors, of the 

 nerves to sweat glands, salivary glands, of the inhibitory 

 fibres to the alimentary canal, and of the cardiac accele- 

 rators, whilst in the terminal ganglia are placed among 

 others the cells on the cardio-inhibitors, on the motor fibres 

 to the lower part of the intestine and bladder, on the in- 

 hibitory fibres to the external genital organs, etc. 



It is also of value to compare the different positions of 

 the cells for analogous fibres to different organs. Treating 

 the vaso-constrictors in this way we see that the cells are 

 placed for the trunk in the corresponding lateral ganglia ; 

 for the upper limb in the ganglion stellatum ; for the lower 

 limb in the sixth and seventh lumbar, and first and second 

 sacral ; for the tail in the coccygeal ganglia; for the stomach 

 in the coeliac ganglion ; for the small intestine in the 

 superior mesenteric ; for the large intestine and rectum in 

 the inferior mesenteric ; for the external genitals in the 



