652 HANDBOOK OF PHYSIOLOGY. 



Spheno-palatine and Submaxillary ganglia. (2) Various ganglia and 

 plexuses of nerve-fibres which give off branches to the thoracic and ab- 

 dominal viscera, the chief of such plexuses being the Cardiac, Solar, 

 and Hypogastric; but inintimate connection with these are many second- 

 ary plexuses, as the Aortic, Spermatic, and Renal. To these plexuses, 

 fibres pass from the prsevertebral chain of ganglia, as well as from cerebro- 

 spinal nerves. (3) Various ganglia and plexuses in the substance of 

 many of the viscera, as in the Stomach, Intestines, and Urinary bladder. 

 These, which are, for the most part, microscopic, also freely communi- 

 cate with other parts of the sympathetic system, as well as, to some ex- 

 tent, with the cerebro-spinal. (4) By many, the ganglia on the Pos- 

 terior roots of the spinal nerves, on the Glossopharyngeal and Vagus, and 

 on the Sensory root of the Fifth cerebral nerve (Gasserian ganglion), are 

 also included as sympathetic-nerve structures. 



Classification. Gaskell's researches have suggested a convenient 

 classification for the sympathetic ganglia into: (1.) The main sympa- 

 thetic chain, extending from above downward, in the form of connected 

 ganglia lying upon the bodies of the vertebrae, which may be called 

 lateral or vertebral ganglia. (2). A more or less distinct chain, praever- 

 tebral in position, consisting of the semi-lunar, inferior mesenteric and 

 similar plexuses, which may be called collateral ganglia. (3.) Ganglia 

 situated in the organs and tissues themselves, called terminal ganglia. 

 (4. ) The ganglia of the posterior roots of the spinal nerves. 



The connection between these parts is as follows: the visceral branch 

 or ramus communicans of each spinal nerve, which is one of the divi- 

 sions of a typical spinal nerve the others being the dorsal and ventral 

 passes first of all into the lateral chain ; from this chain branches, 

 rami efferentes, pass into the collateral ganglia, and from these again 

 other branches pass off into the organs to end in the terminal ganglia. 

 In the thoracic region the rami communicantes are composed of two parts, 

 white and gray. The former can be traced backward into both spinal 

 nerve-roots of their corresponding spinal nerve ; and in the other direc- 

 tion partly into the lateral sympathetic chain, and partly into the great 

 splanchnic nerves and so into the collateral ganglia without entering 

 the lateral chain at all. The upper white rami (from the 2nd to the 

 5th), however, proceed upward and join the' superior cervical ganglion 

 instead of passing downward into the splanchnics. Other branches go 

 downward into the lumbar and sacral plexuses. The gray rami of all 

 the spinal nerves are the only apparent representatives of the visceral 

 branches in the regions above the 2nd thoracic nerve-root, and below 

 the 2nd lumbar nerve-root, with the exception of the roots of the 2nd 

 and 3rd sacral nerves, which have also white rami, and consist of non- 

 medullated fibres, and pass from the ganglia to be distributed chiefly to 



