30 THOMPSON YATES LABORATORIES REPORT 
nerve of the Cat contain some 130 visceral nerve-cells ; and since the fibres are small, the cells are 
probably small also. 
It is curiously difficult to initiate reflex reactions by sensory stimuli applied to the viscera 
themselves. In his great essay on ' The Parts that feel and the Parts that do not feel,' * Albert 
von Haller in the last century brought forward abundant evidence of the extraordinary violence 
of insult that may be inflicted on the viscera even in absence of all anaesthesia — his observations 
were a hundred years prior to the advent of anaesthetics — and yet fail to evoke of sensation any 
sign whatsoever. Certain visceral conditions are, however, well known to be characterised by 
extremity of pain — instance the pain of renal or of biliary colic. In order to examine the 
aflferent channels from viscera, I have had recourse to vascular reflexes obtainable in anaesthetized 
animals, and find they can be strikingly well provoked by the injection of a little fluid into such 
passages as the ureter and bile-duct. The mechanical distension transiently produced by injecting 
a few cubic centimetres of saline solution into the bile-duct immediately and regularly evokes 
a marked rise of arterial pressure. Plate II is an instance of the reactions which occur, typical 
bulbo-spinal reflex actions implicating the vaso-motor system ; vaso-motor spasm of considerable 
intensity, and often presenting a double maximum, succeeds each irritation. 
These reactions seem to offer a means of experimentally determining the exact paths along 
which nervous impulses travel from these viscera to the spinal axis. I hope shortly to finish the 
work I have commenced in that direction ; the results obtained confirm those published by Dr. 
Bradford on the kidney, t and by Dr. Head J on the ureter and other viscera ; from the liver the 
afferent path as regards nerve-roots seems especially wide. Regarding overlap of distribution in 
the viscera neurons lying in adjacent spinal ganglia, little or nothing is known. Of the three 
great sets of channels, vagus, thoracic afferent roots, and sacral afferent roots, it is probable that at 
their boundaries there is some overlapping in their peripheral distribution. 
It has by a number of authorities § been denied that the skeletal muscles possess afferent 
nerves, but analysis of the nerve trunks, entering and supplying the muscles, into their component 
fibres derived from the ventral and dorsal spinal nerve-roots respectively, demonstrates that the 
skeletal muscles receive quite a large number of nerve-fibres that are sensory. These nerve- 
fibres vary much in size, and some of them are the largest afferent nerve-fibres in the body. 
Many of them are, however, very minute, and these last seem to end in relation with the blood- 
vessels of the muscles. The sense-organs in the skeletal muscles are the ' muscle-spindles,' the 
tendon organs of Golgi, the end-bulb-like bodies in perineurium, the end-organs placed at junction 
of muscle-fibre and tendon especially exemplified in the eye muscles, and a few Pacinian 
corpuscles. In the nerves to some muscles the afferent fibres are as numerous as the efferent. It 
is probable that the very largest cells in the spinal ganglia belong to some of the nerve-fibres of the 
muscle-spindles. Probably in every spinal ganglion a number of the nerve-cells belong to the 
sense organs of muscle. 
The topographical distribution of the afferent neurons of the skeletal muscles at the 
* 'Opera Minora,' vol. i, Lausanne, 1772. 
t Foster's 'Journal of Physiol.,' vol. xi, 1891, 
I ' Brain,' 1893. 
§ V. Haller, Schiff, KOihne, &c. 
