THE AUTONOMIC NERVOUS SYSTEM 527 



ganglionic fibre arising in this ganglion and continued generally 

 as a non-medullated fibre to its peripheral distribution. 



This transference from one system to another involves the passage 

 across a synapse and a nerve-cell. The situation of this nerve-cell 

 may be easily revealed by utilising the action of nicotine, first studied 

 by Langley. Tf nicotine be applied to a sympathetic ganglion, it 

 first stimulates and then paralyses any junction between axon ter- 

 mination and nerve-cell which may lie in the ganglion. Intravenous 

 injection of nicotine therefore causes a primary general excitation 

 of all visceral ganglion-cells. There is an enormous rise of blood 

 pressure, which may be accompanied by other sympathetic effects, 

 such as dilatation of the pupil, secretion of saliva, erection of the 

 hairs, and so on. This rise rapidly passes off, and it is then found 

 impossible to evoke any reflex visceral effects or any contraction, 

 e.g. of the blood-vessels, by stimulation of the spinal cord ; the passage 

 of the impulses is blocked in every one of the visceral ganglia. By 

 observing the effects of stimulation of a nerve before it enters a 

 ganglion and then painting the ganglion with nicotine and again 

 trying the effects of excitation, it is easy to determine whether the 

 nerve fibres which were excited in the first case form any connections 

 with the nerve-cells of the ganglion. In the strength in which it is 

 usually applied nicotine is without effect on nerve fibres. 



THE CRANIAL AUTONOMIC FIBRES 



In the course of development the greater part of the fibres of 

 the facial nerve have lost their special visceral functions and have 

 the aspect and functions of ordinary somatic fibres. Visceral fibres 

 are contained in the following cranial nerves the third, seventh, 

 ninth, tenth, and eleventh. 



Third nerve. The visceral fibres of this nerve pass to the ciliary 

 ganglion in the orbit where they end ; the post-ganglionic fibres 

 from this ganglion form the short ciliary nerves which innervate the 

 sphincter pupillae and the ciliary muscles. 



Seventh nerve. The autonomic fibres of the facial arise from the 

 medulla in the intermediate nerve of Wrisberg, which is practically 

 the anterior continuation of the ninth, tenth, and eleventh nerves. 

 From the seventh nerve is derived the chorda tympani nerve, which 

 supplies vaso-dilator nerves to the tongue, the submaxillary and 

 sublingual glands, and secretory fibres to these glands. 



The cell stations of these nerves lie peripherally, those of the 

 sublingual gland in the so-called submaxillary ganglion ; those of 

 the submaxillary gland in the hilus of this organ. It is probable 

 that the seventh sends also pre-ganglionic visceral fibres to the spheno- 

 palatine ganglion, whence a fresh relay of fibres post-ganglionic-- 



