172 ANATOMY AND PHYSIOLOGY 



influence by checking respiration in the way in which 

 it causes the nerve to act upon the muscle in muscu- 

 lar motion/'* 



These remarks appear to harmonise with the prin- 

 cipal facts which have been ascertained respecting 

 this interesting phenomenon, and the nature of the 

 substance by which it is produced. These facts are 

 chiefly the following: the light is subject to the 

 will of the animal ; it becomes more brilliant when 

 its motions are violent ; a certain degree of heat is 

 necessary for its display, and its intensity increases 

 up to 40 R. when it becomes extinct, as it likewise 

 does when the cold is at 10 R. ; oxygen renders it 

 more brilliant for a short time, but soon extinguishes 

 it ; the same effect is produced more speedily by irres- 

 pirable gases, and by placing it in a vacuum ; the 

 phosphorescence soon disappears after the death of 

 the animal, but can be restored by warm water, oil, 

 or alcohol ; galvanic electricity excites it ; and, finally, 

 when the insect is kept for some time in the dark, 

 the luminosity disappears, but is restored by exposure 

 to the light of the sun. 



According to the observations of M. Morren, pro- 

 fessor of botany in the University of Liege, as detailed 

 by Lacordaire, the luminosity of the common Euro- 

 pean Lampyridee is increased in brilliancy by the 

 peculiar structure of the corneous envelope of the 

 phosphorescent matter. It is stated to be mereiy a 

 continuation of the general tegument, become much 



* Burmeister's Manual of Ent. p. 497. 



