348 Comparative Physiology. 



is found that the process of germination may be quickened by 

 connecting the seed with the negative pole of a feeble galvanic 

 apparatus, and retarded by a proximity with the positive. In 

 animals, though electricity seems to possess a peculiar relation 

 with the organic processes, especially muscular contractility, 

 yet no very definite influence seems to be produced by its ex- 

 ternal application to the system. Many tribes of animals 

 appear to be peculiarly affected by changes in the electric con- 

 dition of the atmosphere, and almost every human being may 

 be cognisant of them from his own feelings. The destruction 

 of life by electricity is accounted for by the disturbance of the 

 affinities between the component elements of the body and the 

 destruction of the vital properties of the tissues, especially the 

 nervous. Bodies killed by lightning pass more rapidly into 

 putrefaction than those killed by other means; the decom- 

 position of flesh already dead may be hastened by electrifying 

 it. The ordinary processes of vegetable growth are attended 

 with the evolution of electricity, as proved by the experiments 

 of M. Pouillet, in which seeds had no sooner sprouted and 

 growth commenced, than the gold leaves of the electrometer 

 were separated half an inch from each other. The growth of 

 plants he thinks one of the most constant and powerful sources 

 of atmospheric electricity. Dr. Graves accounts for the violence 

 of meteorological phenomena in tropical islands, by the evapo- 

 ration from the sea rendering the atmosphere positively elec- 

 trical with great intensity during the day, at the very time 

 when terrestrial vegetation is rendering the air negatively elec- 

 trical. Contrary electrical states are produced by the processes 

 of decomposition and recomposition going on in the vegetable 

 juices, and wires placed in the pith, bark, and different places 

 of the plants, and their fruits, denote different states of elec- 

 tricity. Dr. Prout supposes that the small quantities of mineral 

 bodies usually regarded as accidentally present in the vegetable 

 tissues may have an important influence, through electricity, on 

 their properties and actions. The various secretions in animals 

 have been thought to take place from different states of elec- 

 tricity : as acids and gastric juice, in the kidneys and stomach, 

 from positive electricity ; and alkali in the bile and saliva, in the 

 liver and salivary glands, from an excess of negative electricity 

 there prevalent." 



As I before noticed on heat, the source of heat in animals 

 has been ascribed to electricity by some. Electricity, they say, 

 is the power by which nervous influence acts. The electricity 

 developed in the brain is, they assert, transmitted along the 

 nerves and across the muscles, which contract by the tendency of 

 electricity to attraction, and electricity is always accompanied 

 by heat. Sir J. Herschel, on viewing the voltaic pile of De Luc 

 discharging itself at regular intervals as the tension accumulated. 



