THE GREAT 8YMPATSETIC NEBV0U8 SYSTEM. 789 



But sometimes, also, this ramuscule cannot be distinguished, and the sub- 

 sacral cord seems to be abruptly terminated by the filament of com- 

 munication from the last sacral pair. 



Functions.— The functions of the sympathetic are yet but little known, 

 notwithstanding the labours of many physiologists, at whose head must be 

 placed Claude Bernard. In a physiological condition, this nerve possesses 

 an extremely obscure sensibility, but which may become very acute in 

 pathological cases. It conveys to organs the unconscious motor exci- 

 tations originating in the spinal cord; and through the filaments it 

 furnishes to the vessels -the vaso-motor nerves— it holds under its control 

 the circulatory phenomena, especially in the capillary plexuses, causing 

 these canals to dilate or contract, and thus diminish or accelerate the flow 

 of blood in them. By this action on the blood-vessels, it may have a 

 pecondary influqnce on the nutrition of the organs to which these vessels 

 are distributed. 



DIPFEKENTIAI. CHAKACTEKS IN THE OREAT SYMPATHETIC OF OTHEK THAN 

 SOUPED ANIMALS, 



In all the domesticated mammals, the general disposition of the great sympathetic is 

 very similar ; so that there are but few and sliglit dift'erences to note. 



In the Ox, the cervical filament does not arise from the lower extremity of {he 

 superior ganglion, but from its middle portion ; it is divibibie into two or three filaments 

 for a certain distance, after which it lies beside the pneumogastrio. The rumuscule 

 that leaves the lower end of the cervical ganglion is very large, and reaches the division 

 of the ccimmon carotid , that which accompanies the internal carotid artery is also of a 

 considerable size. '^Ruminants have 13 thoracic and 6 lumbar ganglia.) 



In the Dog, the cervical sympathetic cord is closely united with the pneumogastrio, 

 and it is not possible to separate them from each other, as can be done in Solipeds ami 

 Euminants. (In the Carnivora there are 13 thoracic and 7 lumbar ganglia.) 



The Pig has a superior cervical ganglion, which is fusiform and very long ; at its 

 lower extremity it gives off several filaments, one of which lies beside the pneumogastrio 

 in the cervical region, but separates from it to join the middle cervical ganglion , the 

 others pass to the tenth nerve, and are confounded witli it at the ganglionic enlargement 

 it sliows behind the pharynx. At the entrance to the chest, a branch separates from 

 the pneumogastrio, passes along with the axillary arteries, and finally enters the heart. 

 This branch is perhaps formed by the fiUiments of the sympathetic that joined the 

 pneumogastrio at the upper part of the neck. iThe inferior cervical ganglion, according 

 to Leyh, is completely isolated from the thoracic ganglion. The Pig has 14 thoracic 

 and 7 lumbar ganglia. 



COVIPAKISON OF THE GEEAT SYMPATHETIC OF MAN WITH THAT OP ANIMALS. 



It is divided and disposed as in animals. The cervical portion is composed of a 

 superior fusiform ganglion, from which emerge many branches which have been studied 

 with the greatest care. There are described ; 1, Superior or intercranial branches ; 2, 

 External or anastomosing branches with the first four spinal nerves ; 3, Internal or 

 visceral branches, which mix with the pharyngeal and laryngeal filaments of the 

 pneumogastrio ; 4, Anterior or external carotideal branches, which pass to the common 

 carotid and the middle of a small ganglion, the intercarotid ; 5, Posterior, muscular, or 

 osseous branches. All these are present in the Horse. A cervical filament and two 

 inferior gan>rlia — middle and inferior — complete this region, of which there is nothing 

 more to be said. 



The thoraiic portion is absolutely identical in its disposition with that of animals ; it 

 gives rise to a great splanchnic nerve, and terminates in the semilunar ganglia. 



There are no differences to note in the lumbar and sacral portions, which we have 

 described as the pelvic. 

 63 



