256 GENERAL PHYSIOLOGY 



more than any others have elucidated this subject. Radziszewski 

 studied in detail the conditions under which chemical substances 

 exhibit phenomena of phosphorescence, and found that a whole 

 series of organic bodies emit light when they are slowly combined 

 with active oxygen in an alkaline solution. Such bodies comprise 

 especially many fats, ethereal oils, hydrocarbons and alcohols. In 

 many the light appears at ordinary temperatures, in others only 

 upon warming. If, e.g., oleic acid be added to an alcoholic solution 

 of potassium hydrate in a test-tube, a light lasting for a short 

 time may be observed in the dark while the acid is being dis- 

 solved. If, after the light has ceased, a drop of a solution of 

 peroxide of hydrogen be added to the liquid, a clear strip of light 

 is seen to pass through the test-tube along with the drop of 

 peroxide of hydrogen as it falls to the bottom. This is due to the 

 fact that the peroxide of hydrogen gives off active oxygen to the 

 oleic acid. The same phenomenon of light is shown still more 

 clearly when oleic acid is dissolved in pure toluol, which likewise 

 is capable of phosphorescence, and the solution is poured over a 

 piece of potassium or sodium hydrate. The intensity of the light 

 can always be increased by shaking, because the free atoms of 

 oxygen are thus brought more into contact with the molecules of 

 the phosphorescent body. If, e.g., into a glass bulb containing 

 a mixture consisting of equal parts of pure toluol and cod-liver 

 oil (which latter always contains in addition to oleic acid free 

 atoms of oxygen), there be thrown a few pieces of potassium 

 or sodium hydrate, and the whole be gently warmed and 

 placed in the dark, no light is seen at first. But, if the contents 

 of the bulb be gently shaken, there is seen " at once a beautiful 

 light streaming through the whole mass like a flash of lightning." 

 It is in the highest degree probable that the luminosity of 

 living substance depends upon analogous processes. Fats, oils, 

 etc., are wide-spread in living substance, and Panceri believes of 

 certain luminous marine fishes that the liquid fat is the luminous 

 body. Substances that give an alkaline reaction are likewise 

 found everywhere in living substance, and the luminosity of 

 organisms is associated with processes of oxidation. Thus the 

 same conditions are present in living substance as in the experiment 

 of Radziszewski. 



3. The Production of Heat 



The production of heat is much less apparent to the senses 

 than that of light. While we can observe the latter readily in 

 the single cell, the amount of heat produced by the single cell, 

 because of the small size of the object, cannot be measured with 

 our crude instruments for the measurement of temperature. Never- 

 theless, it must be assumed that in the interior of every living cell 



