ANIMAL ELECTRICITY. 283 



The handsome diamond bird represented in the centre of the illustration 

 belongs to Madame de Metternich. When any lady wears it in her hair, 

 .she can, by the concealed wire, make it flap its jewelled wings, and by so 

 doing cause much surprise amongst the spectators. 



We will now endeavour to give a description of the manner in which 

 these toys play their parts in company with the " hermetic-pile " which 

 M. Trouve has applied to many specialities that he has supplied to doctors, 

 who use them largely. 



This pile is formed by a " couple " of carbon and zinc hermetically 

 enclosed in an ebonite box. The carbon and zinc only occupy one-half 

 of the case. The liquid occupies the other. The sketch (fig. 280) on 

 preceding page will explain the apparatus. 



So long as the case is in its normal position the elements are not 

 immersed in the solution, and consequently no electricity is developed. 

 But as soon as the figure is placed in a horizontal or leaning position the 

 force is generated ; on readjusting the box the electric current is cut off, 

 and all development ceases. Many curious electrical toys can be seen in 

 Paris. Dolls are made to talk, and many other wonders for children can 

 be easily procured. 



ANIMAL AND ATMOSPHERIC ELECTRICITY. 



Before concluding the subject of electricity we must devote a few pages 

 to the consideration of the electric influence possessed by certain fishes, and 

 to some of the phenomena of the atmosphere, especially thunderstorms. 

 We have seen how Galvani experimented upon the limbs of frogs, and 

 maintained that they possessed electricity ; he attributed the current in the 

 muscles to that cause. This theory Volta denied, but subsequently Nobili, 

 in 1827, proved the existence of a current in the frog by means of a Gal- 

 vanometer. This was conclusive, and the experiment was performed in the 

 following manner : He filled two vessels with salt and water, and into one 

 ihe dipped the crucal muscles of a frog, and in the other the lumbar nerves 

 were immersed. By putting these vessels in communication with his im- 

 proved Galvanometer, which was extremely sensitive, he perceived a current 

 passing from the feet towards the head of the animal. 



It is, however, to Matteucci and Du Bois Reymond that the investiga- 

 tion of the phenomena of the courant propre are due. The former formed a 

 "" pile " of the thighs of frogs, and by placing the interior and exterior muscles 

 in contact he formed a current from the inside to the outside muscles. This 

 -current is supposed to be occasioned by certain chemical changes which 

 are continually taking place, and it continues longer in the case of a cold- 

 blooded animal than in a warm-blooded one. There are many interesting 

 papers on this subject included amongst the " Philosophical Transactions " ; 

 and the " Physical Phenomena of Living Beings" is fully treated in Matteucci's 

 lectures on that subject. In the "Transactions" for 1848 and subsequent 



