THE SYMPATHETIC NERVOUS SYSTEM. 629 



have not passed through the lateral chain, and which therefore retain 

 their medulla until they reach the proximal or collateral chain. 



c. Glandular Nerve Fibres. A double nerve supply,, in all proba- 

 bility coinciding with the supply to the visceral muscles, has been 

 demonstrated in the cases of the submaxillary, parotid, and lachrymal 

 glands, and in these cases the course of the fibres is very similar to that 

 of the corresponding fibres for the vaso-muscular supply. Thus the 

 sympathetic supply for these glands passes along with the vaso-motor 

 fibres from the cervical splanchnic (or sympathetic trunk), and superior 

 cervical ganglion; whilst the cerebro-spinal supply comes from the rarni 

 viscerales of the cranial nerves in conjunction with the vaso-dilator 

 fibres. 



Central Origin of the Rami Viscerales. There appears to be the 

 strongest presumption that the white rami of the thoracic region arise in 

 the spinal cord in, or are connected with, the cells of the posterior vesic- 

 ular column of Clarke. This conclusion is based upon the fact that 

 these special cells are found in the three regions already mentioned, and 

 in those only where the white rami of fine medullated fibres exist, viz., 

 in the cervico-cranial regions, in the spinal accessory, in the thoracic 

 region, and in the sacral region. But it is probable that the fibres are 

 also connected with the cells of the lateral horn of the gray matter of the 

 spinal cord, and its representative in the medulla, the antero-lateral 

 nucleus of Clarke. 



B. Structure and Functions of the Ganglia. The sympathetic 

 ganglia all contain (1.) nerve-fibres traversing them; (2.) nerve-fibres 

 originating in them; (3.) nerve- or ganglion-corpuscles, giving origin to 

 these fibres; and (4.) other corpuscles that appear free. In the sympa- 

 thetic ganglia of the frog, ganglion-cells of a very complicated structure 

 have been described by Beale, and subsequently by Arnold. The cells 

 are inclosed each in a nucleated capsule: they are pyriformin shape, and 

 from the pointed end two fibres are given off, which gradually acquire 

 the characters of nerve-fibres: one of them is straight, and the other 

 (which sometimes arises from the cell by two roots) is spirally coiled 

 around it. 



According to Gaskell the functions of the main sympathetic ganglia 

 are the following: (1.) They effect the conversion of medullated into 

 non-medullated fibres; (2.) They possess a nutritive influence over the 

 nerves which pass from them to the periphery; (3.) They increase the 

 number of fibres at the same time as they cause the removal of the 

 medulla. As regards their possession of the usual properties of nerve- 

 centres little or nothing is certainly known. It appears unlikely that 

 they possess the reflex functions of the spinal centres. 



Respecting the general action of the peripheral ganglia of the sympa- 

 thetic, in reflex or other actions, little need be said, since they may be 



