SEC. 8. THE LYMPHATIC ARRANGEMENT OF THE 

 BRAIN AND SPINAL CORD. 



517. The Oerebro-spinal Fluid. The specimens of cerebro 

 spinal fluid which have been examined as to their composition 

 are not quite comparable with each other, since while some 

 (such as those obtained from cases where a fracture of the base 

 of the skull has placed the subarachnoid space at the base of 

 the brain, where it is largely developed, in communication with 

 the external meatus, and the fluid escapes by the ear) may be 

 regarded as normal, others (such as those obtained from cases 

 of hydrocephalus where the ventricles contain an unusual quan- 

 tity of fluid, or from cases of spinal malformations) must be 

 considered as abnormal. In most of the more complete analy- 

 ses, .the fluid examined has belonged to the latter class; and 

 the following statements apply, strictly speaking, to them alone. 



With this caution we may say that the cerebro-spinal fluid is 

 a transparent, colourless or very slightly yellowish fluid, of faint 

 alkaline reaction, free from histological elements. The specific 

 gravity is about 1010 or less, the amount of solids being on an 

 average 1 p.c. Of these by far the greater part, -8 or -9 p.c., is 

 supplied by salts, the total quantity of which as well as the 

 relative amount of the several constituents being about the same 

 as obtain in blood and lymph. The comparative deficiency of 

 solids is due to the scantiness of the proteids, which rarely 

 exceed -1 p.c. These are chiefly globulin and a form of albu- 

 mose, or even peptone ; albumin is said to be generally absent. 

 The fluid, save apparently in exceptional cases, does not clot, 

 and contains neither fibrogenous factors, nor fibrin ferment. It 

 very frequently contains a substance which like dextrose reduces 

 Fehling's solution but which is not a sugar ; it appears to be pyro- 

 catechin or a closely allied body. 



Seeing that a fluid of such a composition is of a different 

 nature from ordinary lymph, furnished entirely in the ordinary 

 way, we might be inclined to infer that probably a very large 

 part of the whole mass of the fluid is furnished by the secreting 

 epithelium of the choroid plexus. But it must be borne in 



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