96 



ANIMAL ELECTRICITY. 



sufficient for the development of electricity ; and 

 animal tissues of dissimilar natures, both living 

 and dead, obey the same law as other sub- 

 stances in this respect. For instance, a kind of 

 voltaic pile has been formed by building up layers 

 of muscle and nerve placed one above the other 

 alternately ; (Himlzen :) also by placing one upon 

 another alternate layers of muscular fibre and 

 brain, separated by a porous substance, soaked 

 in salt-water. (Lagrave.) Another such has 

 been made with plates of one kind of metal, 

 fresh muscle, and salt-water, or blood, which 

 acted on the galvanometer. When the con- 

 ductors of a galvanometer (Schweigger's) are 

 armed with plates of platina, on one of 

 which a piece of muscle of a few ounces in 

 weight is placed, and the conductors are then 

 plunged in blood or in a weak solution of salt, 

 a deviation of the magnetic needle of the in- 

 strument is perceptible. (Prevost and Dumas.) 

 The same happens when to one conductor is 

 applied a plate of platiua moistened with mu- 

 riate of antimony or nitric acid, to the other a 

 piece of nerve, muscle, or brain, and both are 

 brought into contact. (Majendie.) Dry piles 

 of considerable electrical power may be formed 

 of organic materials alone, without the interven- 

 tion of metals. If concentrated extracts of 

 organic bodies (animal or vegetable) be spread 

 upon thin paper, and piles be built up of discs 

 cut from this paper, so that two dissimilar layers 

 be separated by two thicknesses of the paper, 

 so much electricity is developed that the elec- 

 trometer is affected. (Kcemtz.) When two 

 persons, both insulated, join hands, electricity 

 is developed sufficiently to affect Coulomb's 

 electroscope. And, if the contraction of mus- 

 cles, the nervous connexion of which with the 

 living body has been destroyed, be considered 

 as a proof that they are subject to the influence 

 of electricity, there are numerous experiments 

 on record tending to prove that electricity is 

 evolved by the mere contact of two dissimilar 

 animal substances. Galvani, Volta, Humboldt, 

 Aldini, Kellie, and Miiller, have all found that 

 when the muscles and the great nerves of a 

 frog's limb are touched synchronously with a 

 piece of the muscle of a warm-blooded animal, 

 weak contractions of the frog's muscles ensue ; 

 and that, when the crural muscles are cut and 

 folded back so as to touch the lumbar nerves, 

 muscular contractions are perceived in the lower 

 part of the limb. Aldini excited most powerful 

 contractions by bringing the nerves of a warm- 

 blooded animal into contact with the muscles 

 of a cold-blooded animal, and vice versa. And 

 Miiller has* further found that contractions are 

 excited by touching the moistened skin of the 

 leg with the nerves of the thigh dissected out 

 and turned down upon them ; the nerves being 

 held by means of an insulating rod.* 



Tiedemann thus states the general results of 

 experiment! such as these. "1. The nerves 

 of the muscles in which it is proposed to excite 

 convulsions must make part of the chain. 

 2. The nerve or portion of nerve which is to 



make part of the chain must be isolated as 

 completely as may be, and no other conductor 

 must produce derivation in this portion of the 

 chain, so as to oblige the electric current, when 

 developed in the chain, to take a course through 

 the nerves. 3. Gttteris parlbus, the convulsions 

 are so much stronger, and are manifested over a 

 greater extent, as the nervous portion, acting as 

 a conductor, enters into the chain. 4. The 

 convulsions are so much more powerful, and 

 last the longer, as the chain is quickly formed, 

 and the surface with which the parts consti- 

 tuting it are in contact is extensive."* And 

 lastly, we now know that even the evaporation 

 of fluids, and changes in the molecular consti- 

 tution of both solids and fluids are always 

 accompanied by electrical excitation. 



Applying these facts to our knowledge of 

 the various processes of the animal oeconomy, 

 we cannot but conclude that, in the course of 

 the many interchanges that are constantly taking 

 place amongst the component particles of all 

 living organs, electricity (perhaps modified by 

 the organic forces) must be developed alto- 

 gether independently of nervous influence. It 

 is certain, however, that electricity flowing from 

 this source is very feebly manifested ; at least it 

 affects our best electrometers in a very incon- 

 siderable degree. Saussure frequently ex- 

 amined the electricity of his own body by 

 means of Volta's electrometer, used along with 

 a condenser, but always failed to perceive any 

 indications of free electricity while he was 

 entirely naked. It was also imperceptible 

 while he perspired freely, and when his clothing 

 was cold. Under other circumstances, he found 

 the electricity of his body sometimes positive, 

 and at other times negative ; but he could not 

 determine the causes of these variations. Simi- 

 lar observations were made by Hemmer of 

 Mannheim in 1786, both on the electricity of 

 his own body, and on that of many other indi- 

 viduals placed in various circumstances. He 

 obtained the following results. 1 . Electricity 

 is developed in all men, but varies in intensity 

 and in nature in different individuals. 2. The 

 character and intensity of the electricity fre- 

 quently varies in the same person. In 2422 

 experiments, it was 1252 times positive, 771 

 negative, and 399 times imperceptible. 3. When 

 the body is at rest and warm, its electricity is 

 always positive. 4. When the surface is much 

 cooled, the electricity becomes negative. 5. It 

 is also negative when the muscular vigour is 

 diminished. More recently this subject has 

 been investigated by Messrs. Pfaff and Ahrens.f 

 They used a gold-leaf electrometer; and the 

 subjects of their observations were insulated. 

 The collecting plate screwed on the electrometer 

 was touched by the person experimented upon. 

 The upper plate of the same was placed in 

 communication with the ground by means of 

 conductors. The results which they thus pro- 

 cured were as follows: 1. The electricity of 

 healthy men is generally positive. 2. Irritable 

 men of sanguine temperament have more free 



* Haudbuch der Phvsiol. dcs Menschcn. Berlin, 

 1833. 



* I'hysiol. trans!, by Drs. Gully and Lane, 270'. 

 t Muckd'a Archiv. iii. 161. 



