357 



THE NERVES, NEUROLOGIA. 



606. The nervous system, sy sterna nervosum, the organ of 

 psychical life, of sensation, and (in reciprocal action with the mus- 

 cular tissue) also that of motion, consists of two principal portions, 

 the central and peripheral, both of which are uninterruptedly united 

 together, and are not even different in substance. The central ner- 

 vous mass is compressed into the cranium and medullary canal of 

 the spine ; the peripheral penetrates (as nerves) the organs of the 

 body, and spreads itself out like the branches of a tree from the 

 central portion. 



607. 1. The tissue of the Nervous system. 



It consists of two portions, opposed to one another, which are 

 found in the nerves as well as in the central portions ; these are : 



608. a. The primitive fibres. They are cylindrical, isolated in 

 their whole course, undivided, with soft, peculiar contents, and sur- 

 rounded by a delicate envelope. In the nerves we observe an 

 external sheath, consisting of fibres of uniting tissue, which, taking 

 a longitudinal direction, are connected with the envelope of the whole 

 nerve, and an internal delicate limiting membrane, which appears 

 to consist of fibres arranged spirally, and closely surrounds the 

 nervous contents (neurine) of the primitive fibre. Both sheaths 

 become transparent by means of dilute acetic acid. The neurine 

 is (in the fresh state) homogeneous, milk-white, soft, readily coagu- 

 lated by cold, alcohol, common salt, &c., and then presents in the 

 middle a central stripe (cylinder axis Purkinje), which is not yet 

 coagulated. In consequence of yielding or laceration, whilst ma- 

 cerating in water, the primitive fibres appear knotty (varicose). 

 In the central parts , the primitive fibres are more delicate, and are 

 not surrounded by an external sheath ; but they are, otherwise, in 

 the same condition as in the nerves. They form the white sub- 

 stance of the former. 



609. b. Ganglion globules (globuli gangliorum), the nucleated 

 bodies of the nerves, form kidney-shaped, three or four-cornered 

 cells, in which is found a clear vesicular nucleus, and within this a 

 nucleolus. The contents of the cell are soft, granular, brownish 

 yellow, or gray. The nucleolus yellowish brown, solid. They 

 are probably surrounded by an internal sheath, but fixed by an 

 external (often reddish) fibrous capsule. They are placed in masses 



