in its Relations to Physiology, 433 



with the master-key — the magic spell — the " open sesame" to unlock all 

 the mysteries of their pursuits. 



Just as at the present day the influence which the application of 

 chemistry will exercise upon the solution of physiological and patho- 

 logical problems is, by many physicians, considered worthy only of 

 ridicule, so formerly were the advantages derivable from chemistry to 

 arts, manufactures, trades, and agriculture, when first indicated, only 

 laughed at by those who were pleased to call themselves practical men. 



It has proved most injurious to science that so many individuals 

 have made experiments without first obtaining any well-defined notion 

 of the design or meaning of experiment. Such people have had the 

 power and the will, but rarely have they proposed any definite object, 

 any well-directed aim ; they have employed a lever, but they have not 

 ascertained the point upon which it turned. The reason that so many 

 experiments have been made in vain, is simply and solely to be ascribed to 

 the fact that comparatively few experimentalists have known how to 

 observe natural phenomena, or understood the import of experimental 

 research. It has been wholly overlooked by them that we do not by 

 experiments examine nature ; we do not study the phenomena them- 

 selves through which nature is manifested to our senses, and experi- 

 ments are only of value inasmuch as they teach us to discover the errors 

 of our inferences and to rectify our false conclusions from observation. 

 If we could climb up to the rainbow, and could maintain the floating 

 r ain-drops in their position until we had concluded our observations 

 and arrived at a correct apprehension of the phenomena, we should not 

 need experiments. But being unable to do this, the philosopher was 

 compelled to have recourse to experiments, to turn and turn a plain 

 smooth, and then a triangular piece of glass for centuries, to measure 

 and to calculate, ere he succeeded at last in apprehending the cause of 

 the colours in the rainbow, their order and relations. 



How admirable is that method, which with such scanty means could 

 lead to the attainment of conclusions so correct as to the nature of 

 phenomena which seemed to lie far beyond our reach ! How much 

 more accessible are those phenomena which plants and animals present 

 to us in their vital processes ! How much easier is the investigation 

 into the conditions essential to life ; the research for causes of disease, 

 states which present themselves daily and hourly to our senses. 



The animal body is as transparent as if made of glass to the intel- 

 lectual eye of the physiologist. He knows definitely and positively 

 the alterations which the air undergoes in the lungs, and yet, neverthe- 

 less, he requires an infinite number of experiments, without the least 



