NATURAL PHILOSOPHY. 189 



the treadmill, is constantly going down under the feet. In ascending 

 a hill, the respiration is greatly increased, and is far greater than 

 arises from muscular exertion on a plain. It would appear that in 

 such muscular action more force or energy is excited by the increased 

 decomposition of the body than is required for the mere mechanical 

 work performed, and that sometimes as much as four-fifths pass off in 

 the form of heat. 



So, also, electricity can be changed into mechanical work ; but in 

 this, as in all other cases, the work performed is only equivalent to 

 the force applied. The philosophers of the last century thought that 

 the vital principle was antagonistic to inorganic laws, and, by suspend- 

 ing their actions, maintained the body in life and health ; but it has 

 been reserved for the present generation to show that the same laws 

 of physical force which are indissolubly linked and correlated in the 

 inorganic world are also the mainspring of the wonderful actional 

 properties of life, and that from chemical and destructive changes the 

 source of the mechanical powers of animated beings is obtained, and 

 which force or energy is never destroyed or obliterated, all organic 

 nature being, equally with inorganic, subjected to one universal con- 

 servation of force. 



HEAPJNG WITH TWO EARS. 

 M. Purkvnie has communicated to the Bohemian Society of 



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Sciences some interesting experiments upon the perception of sound 

 by the ear. Two India-rubber tubes, formed at one end into a hear- 

 ing trumpet, were introduced, one into each oar, and two persons 

 spoke at the same time into the two trumpets. Some time ahvays 

 elapsed before it was possible to distinguish the words on either side, 

 or even on both sides at once. When the tubes had several branches, 

 so that more than two persons could speak at once, it was impossible 

 to understand their words. When two tubes were united into one 

 trumpet, the sound of the voice was heard always as if it existed 

 inside the head, upon whatever side the person speaking was placed. 

 By this means we might examine the relative sensibility of the two 

 ears, for, when they differ, the sound appears to reside in the head, 

 nearer one ear than the other. M. Purkynie thinks that the illu- 

 sion in question may be explained by the structure of the auditory 

 conduit and of other parts of the organ of hearing. With two tunes 

 Communicating with the two ears, M. Purkynie could not succeed in 

 associating two vowels so as to hear a diphthong. But by adapting to 

 one ear a tube with two branches, each vowel associated easily with 

 every other, and diphthongs were heard perfectly. In the same way 

 two sounds, such as s and o, f and a, etc., might be confounded in 

 syllables. Two musical sounds, when heard by the tube, produced a 

 third tone by combination, which appeared to have its seat in the 

 inside of the head. 



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