9 o BIOLOGICAL PHYSICS 



must look to this circumstance for a means of obviating 

 the dangers arising to the functional powers of the impor- 

 tant structures composing the nervous system. Therefore, 

 notwithstanding that we have been taught to consider the 

 cerebro-spinal cavity a " shut sac," we have satisfied our- 

 selves it is not so, because we have discovered in a 

 continuation of our enquiry into the subject of cerebro- 

 spinal lymph circulation, so far as it is applicable to the 

 elucidation of the problem, and in so far as it is required 

 to complete our survey of the nervine circulation, that it 

 is, on the contrary, abundantly perforated and physiologically 

 pervious and porous. 



Moreover, in pursuing these enquiries, we have asked 

 ourselves again and again, is it possible after all that the 

 cerebro-spinal cavity is a " shut sac " ? and have answered 

 ourselves by asking, is it possible after all that the most 

 important organs in the body are suspended in, and inter- 

 penetrated by, a fluid largely composed of their own 

 debris and noxiously impregnated with the toxins resulting 

 from the exercise of their own structures and functions and 

 for which there are no possible outlets available ? To 

 the latter questions we have, therefore, felt constrained 

 to return a negative answer, and, in justification of our 

 unbelief we venture to suggest the following alternative 

 views : 



It was once said that " Nature abhors a vacuum," the 

 saying being elicited from its author under pressure. We 

 would now say, in all spontaneity, that nature also abhors a 

 stasis and toxicity, and delights in the perpetual movement of 

 matter, whether in large or small masses, or whether in 

 molecular, or stellar, manner and proportions, and in an 

 atoxic condition. 



Applying these aphorisms to our consideration of the 

 problem of the disposal of the cerebro-spinal fluid, they 

 enable us to satisfy ourselves that here we are dealing with 

 no exception to the rule of perpetual movement, or circu- 

 lation, in matter, and that we have only to follow it up to 

 find that nature does not interpose blank walls against 

 which that fluid may contend in hopeless imprisonment, 

 but, on the contrary, that she provides a loopholed, yet 

 carefully guarded circulatory receptacle into which it can 



