OF VITAL PHENOMENA 173 



gree during health, this is not at all the case with the lower or- 

 ganisms. The temperature of small marine animals is never 

 more than .7° above that of the medium. The body of an isolated 

 insect may be 4 above that of the air, whereas the temperature 

 in the center of a swarm of bees may be 17° above that of the air. 



Light Production 



Light is produced by bacteria, fungi, protozoa, medusae, cteno- 

 phores, molluscs, fish, Crustacea and insects, and the eggs and 

 larvae of photogenic animals. The sea on a favorable night re- 

 veals a host of wonderful luminous creatures. The effect of 

 myriads of luminous Dinoflagellates in the Pacific is very striking. 

 The water is reddened by day and turned to a sea of fire at night 

 by these protozoa. Spray, the crests of waves and the outlines 

 of fish and bathers are illuminated. The species is Gonyaulax 

 polyedra. 



In all organisms which produce light intermittently, the pro- 

 duction of light follows stimulation with all classes of stimuli. 

 If the production of light is always due to oxidation, it forms 

 a convenient index of the control of oxidation by the organism 

 or cell. When the photogenic organism is crushed, the light is 

 emitted at a rapid rate for a short time. An analogy to this 

 luminescence of the dead organism is seen in "chemilumines- 

 cence" which will now be described. 



It was shown by Callaud and Pelletier that wax, fatty oils, 

 sugar and alkaloids, emit light on being warmed. Radziszewski 

 (1883) showed that these substances even if kept in the dark, 

 and not previously exposed to light, emit light on oxidation with 

 alkaline solutions containing 2 . Besides glucose, gallic acid, 

 etherial oils, cholesterin and lophin, he found that unsaturated 

 fatty acids and compounds containing them may emit light. His 

 list includes oleic, elaidic and ricinoleic acids and their fats and 

 soaps and lecithin, protagon and cetyl alcohol wax. 



It has been pretty clearly established that the production of 

 light by animals and bacteria is dependent on oxidation. Re- 

 cently E. N. Harvey (1914) has dried the photogenic organs 

 of the firefly in vacuo and found that it could be kept in this 

 condition indefinitely and at any time caused to emit light by the 

 addition of water containing 2 . Harvey (1916) obtained from 



