108 PHYSIOLOGY. 



of defence. Sparks also have been seen to attend the dis- 

 charges ; and the shock has been communicated through a 

 chain consisting of several persons with their hands joined. 



13. Common electricity, and that produced by the organs 

 of electric animals, are generally believed to be different, but 

 it has lately been discovered by Dr. Davy, that the electric 

 organs of the torpedo affect the galvanometer, render needles 

 magnetic, and decompose waters 



14. Many animals as well as plants are endowed with 

 phosphorescent properties. Every person almost, has seen 

 rotten wood, or dead fish, shine in the dark ; such are phos- 

 phorescent. ,This phenomenon is probably owing to the 

 fact, that during the decomposition of animal or vegetable 

 matter there is formed a highly inflammable compound of 

 carbon, hydrogen, and oxygen, which like phosphorous, burns 

 at the ordinary temperature of the air, with an evolution of 

 light. 



15. But several living animals exhibit luminous appear- 

 ances. Many of the lower order of animals that inhabit the 

 sea, and some fishes, are phosphorescent.i It is this that 

 causes the luminous appearance of the ocean in warm cli- 

 mates. If a vessel be filled with sea*. water containing these 

 animalcula they immediately become phosphorescent, on 

 shaking the vessel. 



16. It is not uncommon to find insects which have the 

 faculty of phosphorescence in a high degree. It is supposed 

 to reside in a peculiar albuminous principle, secreted by the 

 animal, and that it requires for its manifestation atmospheric 

 air and a certain degree of heat. It is evidently under the 

 control of the animal's will, and probably , depends on the 

 nervous action. Some say, however, that it is a peculiar 

 animal matter secreted at will, which, combining with the 

 oxygen of the air gives rise to the disengagement of light. 



Questions. Have bodies the faculty of regulating their own temper- 



