DIFFERENCES OF CEREBRO-SPINAL NERVES. clvii 



is continued into the covering lamina of connective tissue. On the other hand, 

 Rouget, Kuhne, and most of those who have given descriptions of the organs in ques- 

 tion, maintain that the end-plate is within the sarcolemma, interposed between it 

 and the proper muscular substance. According to their descriptions, the ultimate 

 nerve-fibre, on reaching the muscular fibre, either immediately or after running but 

 a short way on the surface, sends its axis- cylinder through the sarcolemma to spread 

 out into the plate, whilst the primitive (or perhaps perineural) sheath joins the sarco- 

 lemma, and the medullary sheath, which continues on the still dark bordered fibre up 

 to this point, here abruptly ceases. The proper substance of the plate, usually lobed 

 at its circumference (Kuhne), is continuous with the axis-cylinder, and is mostly held 

 to be an expansion of it, for it is said to have the same homogeneous or, at most, 

 faintly granular aspect, and to agree with it in optical and micro-chemical characters. 

 Around and beneath this lamina is a bed of granular matter, with large imbedded 

 nuclei having one or more bright nucleoli. The sarcolemma over the seat of the end- 

 plate, and the plate itself, are slightly raised above the general surface, so that the 

 whole structure has been designated by Kiihne as the nerve-eminence (Nerven-hiigel). 

 It would appear that a muscular fibre has but one terminal organ, and receives con- 

 sequently but one nerve-fibre, so that, allowing the muscular fibre to be one inch and 

 a half long, a considerable length must be governed by one terminal nerve-fibre. As, 

 moreover, the fibres of a nerve undergo division, probably repeated division, before 

 ending, it follows that one fibre in a nerve-root or trunk may supply several muscular 

 fibres. The motorial end-plates have now been recognised in mammalia, birds, and 

 scaly reptiles, and, in a modified form, in various invertebrata. * 



Differences of cerebro spinal Nerves. It remains to notice the differences 

 which have been observed among the cerebro-spinal nerves in regard to the 

 size of their fibres, 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 arrive at an approximate estimate of 

 the relative amount of the large and the small fibres in different nerves, give the fol- 

 lowing as the more important results of their researches. 



1. The nerves of voluntary muscles have very few small fibres, usually in not larger 

 proportion than about one to ten. 



2. In the nerves of involuntary muscles, whether derived immediately from the 

 cerebro-spinal system or from the sympathetic, the small fibres eminently preponde- 

 rate, being about a hundred to one. 



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

 many small as large. 



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

 more small fibres than large : in mucous membranes possessing little sensibility, the 

 nerves are made up chiefly of small fibres. The nerves distributed in the pulp 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 proportion assigned 

 to the small fibres in their estimate must be taken as including some grey, as well as 

 white fibres; and this agrees with the observation previously made by Remak, that 

 many more grey fibres are contained in the cutaneous 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 termination. 



The fibres of the optic nerve for the most part resemble the white fibres of the 

 brain, and readily become varicose. The same is true of the acoustic nerve, from its 



* For further information on the termination of the nerves, see the Croonian Lectures, 

 by Professor Kolliker, Proceedings of the Royal Society, 1362, and by Dr. Beale, ibid., 

 1865 ; also a discussion of the question by Dr. B. in his " Archives of Medicine" for 

 1865. 



