34 THE INVOL UNTAR Y NER VO US S YSTEM 



nerves of opposite function supply the heart, viz. the vagus, which 

 inhibits its action, and the accelerator, which increases its action. 

 Of these two it is generally recognized that the latter corre- 

 sponds to the motor nerves of the blood vessels. The accelerator 

 nerves were traced in warm-blooded animals in Ludwig's labora- 

 tory in 1871 by Schmiedeberg, and were found to proceed to 

 the heart directly from the following sympathetic ganglia : the 

 stellate ganglia, the ganglia on the annulus of Vieussens, and the 

 inferior cervical ganglia. They arise from cells in these ganglia, 

 which were subsequently found to be connected with the central 

 nervous system by connector nerves, which leave the cord in the 

 anterior roots of the upper thoracic nerves and belong therefore 

 to the thoracic outflow (Fig. 4). On the other hand it was asserted 

 for a long time that in cold-blooded animals the vagus nerve was 

 an accelerator as well as an inhibitor nerve, that therefore there 

 was no uniformity in this respect. Feeling sure that this was a 

 mistake I determined to investigate the conditions in an animal, 

 which was cold-blooded, but also to a slight extent warm-blooded ; 

 for this purpose I obtained some live crocodiles and found in them 

 that the accelerator went to the heart from the ganglion stellatum 

 and not from the vagus. I found also the same separation in the 

 tortoise. I then carefully investigated the frog, and found an 

 annulus of Vieussens and the accelerator fibres going off as in all 

 other animals ; but, because they passed to the heart with the 

 vagus, stimulation of the latter nerve necessarily stimulated them 

 too. There is therefore no exception ; the motor cells, from 

 which arise the motor nerves to the heart muscle, are connected 

 with the thoracico-lumbar connector nerves in all cases. 



With regard to the blood vessels, it has been argued that the 

 hypersemia of the lungs and cornea, which follows upon section of 

 the vagus and intra-cranial trigeminal respectively, indicated the 

 section of vaso-constrictor fibres in these two nerves ; but, apart 

 from the fact that there was no evidence of contraction of the blood 

 vessels of these organs when the respective nerves were stimulated, 

 it has been conclusively shown that the hypersemia is the conse- 

 quence of paralysis in the laryngeal region in the one case, and is 

 due to the loss of sensation in the other. The only positive as- 

 sertion of the motor innervation of an unstriated muscle, which 

 may be looked upon as belonging to the vascular system outside 

 the area of the thoracico-lumbar outflow, is Roy's statement that 



