ANIMAL HEAT. 24-7 



The germs of many insects, &c. are unaffected by a great range of tempera- 

 ture. I know a gentleman who boiled some honey-comb two years old, and, 

 after extracting all the sweet matter, threw the remains into a stable, which was 

 soon filled with bees. Body lice have appeared on clothes which had been im- 

 mersed in boiling water. Spallanzani found long ebullition in the open air 

 favourable to the appearance of the animalcules of vegetable infusions ; and the 

 application of great heat in close vessels, although it prevented the appearance 

 of a larger kind of animalcule, did not that of a smaller. The eggs of silk- 

 worms and butterflies hatch after exposure to a cold of 24 below zero. On the 

 other hand, insects may be frozen repeatedly, and recover as soon as thawed, as 

 we shall see when speaking of torpidity. 



Besides the power of generating heat, some animals are luminous, and some 

 display great electric phenomena. v- t 



The glow-worm is known to all ; and many insects of the beetle tribe, as well 

 as others, emit light. Many can extinguish or conceal their light, or render it 

 more vivid, at pleasure. Jn some it has been found to proceed from masses not 

 dissimilar, except in their yellow colour, from the interstitial substance of the rest 

 of the body, lying under the transparent integuments, and absorbed when the 

 season of luminousness is passed. (Consult Kirby and Spence, An Introduction 

 to Entomology, vol. ii. p. 409. sqq. ) The ocean is frequently luminous at night 

 from the presence of certain animalcules, to some sort of which, perhaps, is owing 

 the phosphorescence of dead herrings. Some fish, as the gymnotus electricus and 

 torpedo, give electric shocks, and possess a regular galvanic battery. 



I have adopted the common language in speaking of animal heat, as though 

 the phenomena depended upon a specific substance. However, there may be 

 every reason to believe that neither caloric nor light are fluids, but peculiar 

 states only ; and electricity may prove to be so likewise ; and, perhaps, all these 

 to be modifications of the same state. 



