INTRODUCTION 9 



In fact, the principles thus established by a host of 

 workers in many lands, were successfully applied to anti- 

 cholera vaccinations by Haffkine, a pupil of the great 

 Louis Pasteur, in 1894, thus overcoming another dread 

 terror of humanity. 



These results were obtained from dealing with things 

 we can see and handle — that really come under the 

 senses. But what are we to say about other nonseeable 

 things we know exist, though we cannot bring them 

 under our limited spheres of sense? 



Under this heading one may mention those colors, 

 such as the infra-red and ultra-violet rays which no 

 human eye can see, but which we can prove actually 

 exist in any physical laboratory. If we turn these rays, 

 invisible to man, upon a group of brown ants, they imme- 

 diately sense them, for they scamper away hurriedly. 

 How do these ants sense that which we cannot? We do 

 not know. 



Such experiments, however, show us why men come to 

 some interesting and remarkable conclusions which would 

 otherwise be extremely difficult to understand. 



From such findings, the late Professor A. D. Darbishire^ 

 came to the conclusion that there must be a great many 

 colors which the human eye cannot see, and many sounds 

 which the human ear cannot hear. Therefore, just insofar 

 as we accept any plausible physical theory which fits into 

 every angle of our mind, should we be the more suspicious 

 of it. Such a theory may fail to take into account the thou- 



