BIOLOGY. 277 



combination of forces which together retain a body in a state of 

 rest, because a merely inert body would be readily overcome by 

 an amount of any. force vastly inferior to that which is able to op- 

 erate upon a living body with impunity; therefore this force is 

 sotucthing more than vis inerticB. 3. This force is convertible 

 into and correlative with the other physical forces, because vital- 

 ity is directly convertible into heat and electricity, and since heat 

 and electricity are convertible into and correlative with all the 

 other physical forces, therefore vitality also is convertible into and 

 correlative with all the other physical forces. 



EFFECTS OF LIGHT ON VITALITY. 



In a paper addressed to the French Academy of Sciences, Dr. 

 Dubrunfaut examines the effects of light on vegetable and animal 

 life. The researches of MM. Gratiolet, Cloez, and Cailletet have 

 in a great measure proved that the red rays of the luminous spec- 

 trum are those to which the important physiological function ex- 

 ercised by the sun on plants is to be exclusively attributed. The 

 leaves in this case act as analyzers of white light; they reject the 

 green rays, which constitute the physical complement of the red 

 ones ; and it is thus the various hues under which the organs of 

 vegetation are seen by us may be explained. If plants were ex- 

 posed to green illumination only, that would be tantamount to 

 their being in the dark. But this kind of light, which the vegeta- 

 ble kingdom refuses to absorb, is precisely that which is coveted 

 by the animal one. Red, the complementary color of green, is 

 that which, owing to the blood, tinges the skin of the healthy hu- 

 man subject, just as the green color of leaves is the complement 

 of the one they absorb. From this principle, so fully established 

 by experiment, M. Dubrunfaut passes to its practical application 

 to domestic life. All kinds of red should be proscribed from our 

 furniture, except curtains. Our clothes, which in point of fact 

 play the part of screens, should never be green, while this color, 

 on the contrary, should predominate in our furniture, its comple- 

 mentary one being reserved for our raiment. In the same way ho 

 contends that the salubrious influence of woods and forests is a 

 luminous and not a chemical eft'ect. In support of these views he 

 mentions cases of patients whose broken constitutions were re- 

 stored merely by long exposure to the sun in gardens deprived of 

 trees or other obstacles to light; he quotes the instance of four 

 children that had become chlorotic b}'- living constantly in one of 

 the narrow streets of Paris, and that regained their health under 

 the beneficial influence of the solar rays on a sandy sea-coast. — 

 Scientific American. 



INFLUENCE OF COLD ON THE NERVOUS FUNCTIONS. 



According to Dr. B. W. Richardson, the phenomena observed 

 on freezing the animal tissues depend essentially on a change in 



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