ON CEREBRO-SPINAL LYMPH 



73 



valves, excretory organs, or eliminatory mechanisms, which 

 are found more or less abundantly distributed in the skin, 

 the mucous and serous membranes, and the muscular 

 structures, as well as viscera. Moreover, in the structures 

 known as the olfactory nerve mechanisms, the pituitary 

 and pineal glands, and the coccygeal glomerulus, with 

 their associated outfall tubular arrangements and organisms, 

 we discover structures whose conjoined functions, besides 



FIG. 7. 



FIG. 8. 



FlG. 7. TWO PORTIONS OF MEDULLATED NERVE FIBRES, AFTER TREAT- 

 MENT WITH OSMIC ACID, SHOWING THE AXIS-CYLINDER, AND THE 



MEDULLARY AND PRIMITIVE SHEATHS. (Key and Retzius. ) 



A, Node of Ranvier. B, Middle of an internode with nucleus. 



c, axis-cylinder, projecting at the broken end ; /, primitive sheath within which the 

 medullary sheath, which is stained dark by the osmic acid, is somewhat retracted. 



FlG. 8. -PART OF AN AXIS-CYLINDER, HIGHLY MAGNIFIED, SHOWING THE 



VARICOSE FIBRILS COMPOSING IT. (Max Schultze.) 



the disposal of the more solid nerve debris, largely consist 

 in regulating the incidence of intra-cranial and intra-spinal 

 pressure, by affording a ready, albeit manifoldly guarded 

 and regulated means of exit to the cerebro-spinal fluid. 

 By these means and a vaso-motor controlled blood- 

 circulation, sensitive to inward and outward circumstances 

 and necessities, an atmosphere, so to speak, of cerebro- 

 nervine calm and repose is maintained amid the most 

 changing conditions of an ever-fluctuating environment. 

 Besides the somewhat mechanical role here described as 



