THE CHEST, ITS CONTENTS AND CONNECTIONS. 45 



This latter is the nerve of sensation, the otlier the nerve of 

 motion ; and thus, though united together, the filaments are yet 

 distinct, and a part is endowed mostly with sensation, or with 

 motion, according as the filaments of the former or the latter 

 predominate. There is one other nerve that remains to be 

 noticed ; it has been called the Ganglial, and also the Sympa- 

 thetic. " It belongs," observes Mr. Youatt, in his admirable lec- 

 tures, " neither to the cerebral nor the spinal system, and seems, 

 in its function, to be independent of both. At the base of the 

 cranium, and in front of the atlas, I find a pyriform reddish body, 

 which gradually contracts, and terminates in a nerve. I inquire 

 not now into the origin of this ganglion, but a superficial glance 

 at the nerve tells me that it is performing some important office. 

 It is connecting itself with the cerebro-spinal, and with every 

 cervical nerve ; but, more particularly, it is forming complicated 

 plexuses on every neighbouring blood-vessel. I trace it particu- 

 larly on both the external and the internal carotid, and I follow 

 it in the subdivisions of these vessels, until, from the minuteness 

 of the vessel, and the pulpiness of the nerve, it eludes my sight. 

 Hereafter I shall have to trace the course of the nerve in the 

 thoi'ax, forming, with the cerebro- visceral, a plexus, or rather, 

 an investing membrane, around every vessel of the heart and 

 lungs ; and then, having reached the abdomen, and combining 

 in the semilunar ganglion its own influence with that of the 

 cerebro-visceral and tlie phrenic, it becomes the seat or centre 

 of organic nervous power, diffusing its radiations over every ar- 

 tery and absorbent, and gland, and ganglion ; every thing con- 

 nected with secretion, nutrition, and life ; itself the very principle 

 of life and action — the soul of the organic system. It was 

 termed, before its character and power were suspected, the sym- 

 pathetic nerve, because it seemed to connect the whole system 

 together: it is denominated by others the ganglial nerve, from 

 its supposed origin, either in the superior cervical or the semi- 

 lunar ganglion ; but it would more properly be designated the 

 great organic nerve, ■ — the secretory, nutritive, chemical, — while 

 the cerebro-visceral is the motor organic nerve. It is the power 

 which presides over, and effects the clianges in that fluid which 

 the motor nerve keeps in circulation." — Ed. 



CHAP. X. 



THE CHEST, ITS CONTENTS AND CONNECTIONS. 



The formation of the chest of the horse is very different from 

 that of the human subject. It is shaped very much like a ship. 



