BEYOND THE LIMITS OF VISION. 13 



Epidemic and contageous diseases are now recognized and 

 treated as produced and propagated by living organisms. Our 

 systems of quarantine and disinfection are founded on this theory. 

 In the case of most of these diseases, there has been discovered 

 and described the veritable bacteria or bacillus which is the cause 

 and virus of each. But still there are some, including malarial, 

 yellow and typhus fevers, equally well known to be germ-diseases, 

 the cause or contagium of which has never been discovered, 

 although you may be sure it has been diligently sought for. 

 These diseases have their regular periods of growth and culmi- 

 nation, of intermittence, or relapse and repetition. "We know 

 that there is something in them that grows and dies ; but what it 

 is no power of the microscope has yet revealed. In this case 

 then, both the germs and the full grown product of the germs are 

 below the limit of magnified vision. 



Evidently the scale of life does not stop at or near the limit 

 which the present state of the optician's art prescribes to the 

 extent of our vision. And there is no assignable reason why it 

 should. The smallest living creature that has ever been seen 

 under the glass, has at least a million million units to work with. 

 But it may be a million times smaller, and yet have the very 

 respectable number of a million structural units, infinitesimal 

 bricks, with which to build its simple little house of a single 

 room. 



So you see there is the easy possibility, and even probability, 

 of another realm of the living kingdoms far below the reach of 

 the microscope. And in strong corroboration of this conclusion, 

 is the fact, as shown by the beautiful experiments of Professor 

 Tyndall, that the blue color of both the sea and sky is produced by 

 an infinite number of minute, and as he thinks organic, particles 

 suspended therein, much smaller than the wave lengths of light, 

 which are on the average about the one fifty-thousandth of an 

 inch. 



If you take a glass jar full of pure distilled water, which is 

 perfectly colorless, and while stirring let fall into it a drop or 

 two of a solution of resin or gum mastic in alcohol, you will have 

 a liquid slowly passing from pellucid water into the most beauti- 



