208 



INNERVATION. 



[CHAP. vin. 



Albumen 

 Cerebral fat 

 Phosphorus 

 Osmazome and Salts 

 Water 



100-00 100-00 100-00 100-00 100-00 



A careful comparative analysis of the vesicular and fibrous mat- 

 ter is as yet a desideratum. We are ignorant of the nature of 

 the colouring material of the former. John states that the vesi- 

 cular substance is deficient in white fatty matter, and that its 

 albumen is less tenacious than that of the fibrous substance. 



Of the Fibrous Nervous Matter. Of the two kinds of nervous 

 matter, the fibrous is that which is most extensively diffused 

 throughout the body. It not only forms a large portion of the 

 nervous centres, either alone or mixed with vesicular matter, but 

 it is the principal constituent of the infinite multitude of nerves 

 which connect them with the various tissues and organs. 



The structure of the fibrous matter should be examined in a 

 piece of nerve, and in a thin section from the white part of a 

 nervous centre, as the brain or spinal cord. These should be torn 

 with needles, so as to separate and isolate as much as possible the 

 elementary parts, and to remove, as far as may be practicable, 

 extraneous tissues. 



The fibrous nervous matter, wherever it is found, consists of fibres 

 which have a definite arrangement. Two kinds of primitive fibre 

 are present in the nervous system, and these we shall distinguish 

 as the tubular fibre, or the nerve-tube, and the gelatinous fibre. 

 The former are infinitely the more numerous; the latter being 

 found chiefly in the sympathetic system. 



1 . Of the Tubular Fibre. When a nerve-tube is perfectly recent, 

 and unaffected by reagents, it presents, if viewed by reflected light, 

 a beautiful pearly lustre, and appears to be quite homogeneous. 

 But if viewed by transmitted light, and with a sufficient magnifying 

 power, a more complicated structure becomes visible in all the 

 largest and best marked specimens (fig. 52, A, E, and fig. 53, a). 

 Most externally is the tubular membrane (A, d d\ an homogeneous, 

 and probably elastic tissue of extreme delicacy, analogous to the 

 sarcolemma of striped muscle (p. 155), and according to our obser- 

 vation, not presenting any such distinct, longitudinal, or oblique 

 fibres in its composition as have been described by some writers. 





