162 AN INTRODUCTION TO ZOOLOGy. 



animalj and sometimes occurs in decomposing animals, 

 such as lobsters and some kinds of fish that are not 

 known to be phosphorescent in the live state. There 

 is considerable variety in the colours shown by phos- 

 phorescent animals of different kinds. The most 

 common colour is a golden light, with a greenish 

 change ; and some creatures change colour when they 

 are disturbed. It is exceedingly probable that the 

 occurrence of phosphorescence is to some extent 

 governed by climatic conditions. Some instances 

 are related of phosphorescence which is of the nature 

 of fluorescence ; i.e., the animal only shines when it 

 has previously been shone upon by the suri, or other 

 bright light ; possibly this is often the case. 



The relations of electric phenomena to the ordinary 

 activities of living bodies are equally obscure with 

 those of phosphorescence. There is a popular idea 

 that the force exercised by nerves, especially the 

 motor nerves, is closely connected with electricity — an 

 idea that is based chiefly on a popular knowledge 

 of experiments of the class that bear the name 

 of their discoverer, Galvani. Aloysius Galvani, a 

 doctor in Bologna (or, according to one version of 

 the story, his assistant), was working with an electric 

 battery, while some dead frogs, intended for culinary 

 purposes, were lying on the table near it ; and one of 

 them received an accidental induction shock, which 

 caused it to exhibit muscular movements. I should 

 think that one of the ensuing results must have been, 

 that the Galvani household never ate frogs again ; 



