THE CAUSATION OF DISEASE. 7 



balance placed in vacuo ; let all friction be removed, and then 

 let us suspend from each arm a ton weight. There will be 

 perfect equilibrium. If now, a grain weight be added to one 

 of these ton weights, the latter, we can assert positively, will 

 descend with a certain degree of momentum. Now, it would 

 be vulgarly said that the particular grain is the cause of the 

 descent, for, the two ton weights exactly balancing one another, 

 the grain will fall to the earth as it would do if left unsup- 

 ported in vacuo ; but, as a matter of fact, every other grain in 

 the descending ton weight takes an equal share in pulling it to 

 the earth j and, if the slightest particle be removed from the 

 other ton, the result, as expressed in terms of momentum, will 

 be modified, and the same will happen if the slightest friction 

 be added. We cannot, therefore, refer the cause of descent 

 to any one particular grain of matter ; the sum of the material 

 conditions of our conception constitutes the cause. 



Secondly, as regards atomic and molecular effects. In the 

 above examples we are dealing with gross material conditions, 

 with obvious and palpable matter — matter, that is, which is 

 capable of being recognized as such by the senses. But beneath 

 the world of our every-day life there is a world of the infinitesi- 

 mal. Our senses take cognizance of quantities ranging within 

 very narrow limits, and although the intellect can reason with 

 vast and infinitesimal quantities, our knowledge of quantity above 

 and below a certain narrow range is merely symbolical — that 

 is to say, we can only represent it by symbols — it is beyond our 

 realization. Let us remember that this difficulty of conception 

 in respect of quantity is not confined to the immense. We 

 are apt to forget this, unmindful of the fact that a second is 

 split up into billions of parts by a vibration of the violet 

 ray of the spectrum, and that the atomic particles of a proto- 

 plasmic cell may be as small in comparison with the cell as is 

 this latter in comparison with our earth. Knowledge (I use the 

 term advisedly, assuming that we can measure such quantities 

 accurately) of this kind is only symbolical; but because our 

 senses are thus limited in range, we must not turn in disdain 

 from the subject, but rather try diligently — let the success be 

 never so slight — to form some faint conception of these infi- 

 nitesimal quantities. 



