PHILOSOPHY OF ZOOLOGY. 



Urinary concretions have likewise been detected in the 

 horse, ox, sow, dog, rabbit, cat and rat. In none of these, 

 however, has any trace of uric acid been detected. In all 

 of them the base is lime, or magnesia, united with phospho- 

 ric, carbonic, or oxalic acids. 



CHAP. XIV. 



PECULIAR SECRETIONS. 



UNDER this head, it is our intention to consider the cir- 

 cumstances under which light, electricity and caloric, are 

 generated in the animal system. The subject is exceed- 

 ingly interesting, and it has been enriched by numerous 

 observations, the united efforts of the naturalist and che- 

 mist. Still, however, there prevails a considerable diversi- 

 ty of opinion, respecting the manner in which these sub- 

 stances are produced, or the share which the vital princi- 

 ple contributes towards their developement. As these bodies 

 frequently appear to be produced contemporaneously, in the 

 changes to which matter is subjected, they are to be view- 

 ed in this chapter in connection, in expectation that the 

 mode of production of one, may help to illustrate the ori- 

 gin of antoher. 



I. LUMINOUSNESS OF ANIMALS. 



THK faculty of emitting light does not appear to be pos- 

 sessed by any individuals of the classes Mammalia, Birds or 

 Reptiles. Several fishes, however, exhibit this remarkable 

 property ; particularly the Dorado, Mullet, Herring and 

 Sprat. The Sparus clirysurus, an inhabitant of the seas 

 of Bra/il, is said to be luminous in such a remark- 



