158 NESVOUS TISSUE. 



throughout the muscular substance, with which they are closely incoriiorated 

 (Sitz. der Phys. Med. Soc. z. Erlangen. 187;)). Another observer. Arndt. who 

 admits the existence of the end-plate, describes in addition a complex system of 

 communicating fibres which extend throughout the muscular substance, and by 

 means of which the plate is brought into connection wit^i the muscle corpuscles 

 and nuclei (Schultze's Archiv f. micr. Anatomie, ix.). 



Diiferences of cerebro-spinal nerves. — It remains to notice the 

 difierences which liave been observed among the cerebro-spinal nerves 

 in regard to the size of their libres, and the proportionate amount of 

 the different kinds of fibres which they respectively contain. 



As already stated, both white and grey fibres exist in cerebro-spinal nerves, and 

 those of the former kind differ greatly from each other in size. Volkmann and 

 Bidder, who have bestowed much pains in endeavouring to amve at an approxi- 

 mate estimate of the relative amount of the large and the small fibres in different 

 nerves, give the follo\\'ing as the more important results of their researches. 



1. The nerA'es of voluntary muscles have very few small fibres, usually in not 

 larger proportion than about one to ten. 



2. In the nerves of involuntai-y muscles, whether derived immediately from 

 the cerebro-.siiinal system or from the sJ^npathetic, the small fibres eminently 

 preponderate, being about a hiuidred to one. 



3. The nerves going to the integuments have always many small fibres, at least 

 as many small as large. 



4. Xeiwes of sentient parts of mucous membranes have from five to twenty 

 times more small fibres than large : in mucous membranes possessing little sensi- 

 bility, the nerves are made up chiefly of small fibres. The nerves which enter 

 the cavities of the teeth consist principally of large fibres. 



It is plain, however, that Volkmann and Bidder must have reckoned in with 

 their small fibres more or fewer of the non-medullated sort, so that the propor- 

 tion assigned to the small fibres in their estimate must be taken as including 

 some grey, as well as white fibres : and this agrees wdth the observation pre- 

 viously made by Remak. that many more grey fibres are contained in the cuta- 

 neous than in the muscular nerves. The roots of the spinal nerves contain fine 

 fibres, but according to Remak only in very small proportion : Volkmann and 

 Bidder state that in man the anterior roots contain proportionally more large 

 fibres than the posterior. In almost all nerves, the fibres diminish in size as they 

 approach their teiinination. 



The pecnliarities of some of tlie cranial nerves, such as the olfactory 

 and auditory, have been already alluded to and need not be further 

 considered here. 



OP THE SYMPATHETIC OR GANGLIONIC NERVES. 



This name is commonly applied to a nerve or system of nerves 

 present on both sides of the body, and consisting of the following 

 parts, viz.: — 1. A series of ganglia, placed along the spinal column by 

 the side of the vertebras, connected with each other by an intermediate 

 nerve-cord, and extending upwards to the base of the skull and down- 

 wards as far as the coccyx. This principal chain of ganglia, with the 

 cord connecting them, forms what is often named the trunk of the 

 sympathetic. 2. Communicating branches, which connect these ganglia 

 or the intermediate cord with all the spinal and several of the cranial 

 nerves. 3. Primary branches passing off ft'om the ganglionic chain or 

 trunk of the nerve, and either bestowing themselves at once, and gene- 

 rally in form of plexuses, on the neighbouring blood-vessels, glands, 

 and other organs, or, as is the case with the greater number, proceeding 



