546 



PRIMITIVE MEDULLARY NEURINE. 



Fig. 215.* 



state ; the same adopted by Gall, Spurzheim, Reil, and others^ 

 in the present century, by whom the anatomy of the brain, 

 though still very imperfect, has been greatly advanced. 

 In the medullary neurine, when examined with the micro- 

 scope, no globules of considerable size and detached distribu- 

 tion, like those of the gray matter, are ever met with. Whether 

 examined in the brain, spinal marrow, or white nerves, it pre- 

 sents, when separated into its ultimate elements, the appearance 

 of parallel white fibres (studded here and there with minute 

 nerve cells,) the diameter of which, according to R. Wagner, is, 

 in the nervous cords, the g^th part of a line. 



These primitive fibres are simple 

 threads, formed of a cylindrical sheath, 

 filled with the nervous matter. This 

 nervous matter or neurine, forms during 

 life a transparent colorless oil-like fluid. 

 It coagulates after death, and then pre- 

 sents the white opaque curdy appear- 

 ance with which all anatomists are 

 familiar. Each one of these fibres, 

 according to the elaborate investigation of Ehrenberg and Muller, 

 however frequently they may cross each other, or appear to 

 unite, whether they are rolled up in separate bundles as in the 

 nerves or penetrate in masses through the ganglia or through 

 the substance of the brain, never unite or do more than come in 

 close apposition with one another ; every where being kept sep- 

 arate by their neurilematic sheaths, which insulates them as 



* Fig. 215. Minute structure of nerve (from Wilson). 1. The mode of 

 termination of nerve-fibres in loops ; three of these loops are simple, the fourth 

 is convoluted. The latter arrangement is found in situations where an exalted 

 degree of sensation exists. 2. A nerve-fibre from the brain, where the neuri- 

 lematous covering is very thin, showing the varicose appearance produced by 

 traction or pressure. 3. A nerve-fibre enlarged to show its structure viz. a 

 tubular enveloped, and a contained substance, neurine. 4. A nerve cell or 

 granular globule of cineritious neurine, showing its composition to consist of a 

 granular looking capsule, and granular contents. 5. Its nucleus containing a 

 nucleolus. 6. A nerve cell from which several caudate (or tooth-like) processes 

 are given off. It contains like the preceding, a nucleated nucleolus. 7. The 

 third constituent of the medullary masses, namely, granules or rather minute 

 cells. These are dispersed among the cerebral fibres in great numbers j they 

 present every variety of size and are many of them nucleated. 



