GANGL ION CELLS LX THE HEAR T. 201 



qualifications to the one and not to the other. One possibility remained, 

 namely, that the ganglion of the inhibitory system, which corresponded 

 to the ganglion stellatum, etc., of the augmentor system, was not to be 

 looked for in the intrinsic ganglia of the heart, but in the ganglion 

 trunci vagi, and that the intrinsic ganglion cells formed a still further 

 ganglionic system upon which both sets of nerve fibres could act. This 

 seemed possible, because, on the one hand, I had shown clearly 

 that this o-ano-lion in the crocodile, which in this animal is situated at 

 the entrance of the thoracic region, is a motor ganglion, from some 

 of the cells of which the terminal motor nerves to the oesophagus and 

 stomach arise ; and, on the other hand, that the fibres of the short ciliary 

 nerves are mednllated, although thev are the terminal nerves of those 

 cells in the ciliary ganglion, which are the motor cells of the fine 

 medullated fibres of the third nerve. It seemed, therefore, plausible that 

 the cardiac fibres of the vagus might enter the heart as fine medullated 

 fibres, even though they were connected with cells in the ganglion trunci 

 vagi. This question received its answer 1 by means of section of the 

 vagus nerve in the crocodile, in the neck, between therefore the ganglion 

 jugulare and ganglion trunci vagi, and subsequent degeneration of the fibres. 

 I then found that, whereas after periods varying from twenty -five days to 

 three hundred days, stimulation of the peripheral end of the cut nerve in 

 the neck produced neither inhibition nor contraction of the oesophagus, 

 stimulation of the nerve peripheral to the ganglion caused as good a 

 contraction of the oesophagus as before, but no sign of any inhibitory 

 effect upon the heart. This experiment conclusively proved that the 

 cardiac fibres of the vagus did not connect with any ganglion cells of the 

 ganglion trunci vagi, and further that the cells on the course of a motor 

 visceral nerve were nutritive to the fibres in the peripheral direction 

 only. I was also able in the dog to trace those fine medullated fibres, 

 among which the inhibitory fibres must have been, from the accessory 

 roots of the vagus, past the ganglion jugulare into the ganglion trunci 

 vagi, without a possibility of the presence of any ganglion cells on that 

 part of their course, so that we may say with certainty there are no 

 efferent cells on the course of the cardiac fibres of the vagus nerve, 

 until we reach the intrinsic ganglia of the heart, such as Eemak's 

 and Bidder's ganglia and the other ganglion cells found on the 

 course of the nerve fibres in the heart itself. Finally, Langley's 2 

 experiments with nicotine have shown that the action of this drug 

 is to break the connection between the efferent medullated fibre from 

 the central nervous system or pre-ganglionic fibre and its vagrant nerve 

 cell, while it does not impair the action of the processes from the 

 nerve cell to the muscular tissue, i.e. the post-ganglionic fibres; and 

 by a series of such observations, he has come to the conclusion that 

 each efferent visceral nerve possesses upon its course, from the central 

 nervous system to its termination in the peripheral tissue, one and 

 only one nerve cell. 



Taking into consideration also the recent investigations of Ramon y 

 Cajal and others, 3 as to the connection of nerve fibres with nerve cells, 



1 Gaskell, "On the Structure, Distribution, and Function of the Nerves which innervate 

 the Visceral and Vascular System," Journ. Physiol., Cambridge and London, 1885, vol. vii. 

 p. 22. 



2 Langley and Dickinson, Journ. Physiol., Cambridge and London, 1890, vol. xi. pp. 265 

 and 509 ; Langley, ibid., vol. xi. p. 123 ; Langley and Anderson, ibid., vol. xiii., etc. 



3 See article on the " Nerve Cell " in this volume. 



