ON THE POSTERIOR GLANDULATURE 109 



of each individual nerve fibril. The physical necessity for 

 this provision at once becomes apparent when we consider 

 the delicate nature of the structures enclosed, compre- 

 hending, as they do, the insulated producers, storers and 

 conductors of nerve force, and the machinery of intelligence, 

 motion, and will structures, therefore indicating the vital 

 importance of preventing the injurious influence and con- 

 sequences of external disturbances reaching them. 



Histologically the continuity of the structures within 

 which the cerebro-spinal fluid is enclosed can be traced 

 from the cranial cavity, the bony wall of which is lined 

 by a series of membranes, each of which accompanies the 

 spinal cord into the spinal canal (or cavity), and thereafter 

 spreads itself around or ensheaths every nerve trunk as it 

 leaves that canal (or cavity), thereafter still travelling with 

 it until it finally loses itself in the terminal extremities 

 of the peripheral nerve fibrils, sensory and motor. These 

 coverings (or sheaths) being thus omnipresent throughout 

 the whole nervous system, it follows that the fluid enclosed 

 within them must also be continuous with its environ- 

 ments and likewise omnipresent, and therefore that it can, 

 and must, exercise the mechanical offices of buffer and 

 protector throughout its whole extent. 



We therefore again express our disbelief in the doctrine 

 of the " shut sac," as applied to the lining of the 

 cerebro-spinal cavity, and reaffirm our conviction of " the 

 truth " of what we have attempted to make clear, 

 summing up our contentions in the expression once more 

 of our belief: circulatio circulationum omnia circulatio. 



Thus we see that the neural lymph circulation, while it 

 belongs to a different order from the haemal lymph 

 circulation, may still be described as a part of the great 

 lymph circulation. It is carried on centrally through the 

 ventricles and central canal, the sub-arachnoid and sub-dural 

 spaces, and peripherally mainly along or between the 

 encircling neural coats epi, peri, and endo beginning in 

 the cerebro-spinal cavity and terminating respectively in the 

 skin, the muscles, and the sympathetic nerves the first 

 through the sensory nerve terminals, and the second through 

 the motor, the latter becoming ultimately directly united 

 with the great sympathetic or haemal lymph circulation. 



