96 EXTERNAL CONDITIONS OF VITAL ACTIVITY. 



infer that this excitement is useful to the process of Vegetation in gene- 

 ral, or that the same kind of electric excitement universally operates to 

 the benefit or injury of the Plant. From some experiments recently 

 made it would appear, that potatoes, mustard, and cress, cinerarias, 

 fuchsias, and other plants, have their development, and, in some in- 

 stances, their productiveness, increased by being made to grow between 

 a copper and a zinc plate, connected by a conducting wire ; while, on 

 the other hand, geraniums and balsams are destroyed by the same in- 

 fluence. The transmission of a series of moderate sparks through plants, 

 in like manner, has been found to accelerate the growth of some, and to 

 be evidently injurious to others. It is not unreasonable to suppose, 

 that, as a great variety of chemical processes are constantly taking place 

 in the growing plant, an electric disturbance, which acts as a stimulus 

 to some, may positively retard others ; and that its good or evil results 

 may thus depend upon the balance between these individual effects. 

 This would seem the more likely from the circumstance, that, in the 

 process of Germination, the chemical changes concerned in which are of 

 a simpler character, Electricity seems to have a more decided and uni- 

 form influence. The conversion of the starch of the seed into sugar, 

 which is an essential part of this change, involves the liberation of a 

 large quantity of carbonic, and of some acetic acid. Now as all acids 

 are negative, and as like electricities repel each other, it maybe inferred 

 that the seed is at that time in an electro-negative condition ; and it is 

 accordingly found that the process of germination may be quickened, by 

 connexion of the seed with the negative pole of a feeble galvanic appa- 

 ratus, whilst it is retarded by a similar connexion with the positive pole. 

 A similar acceleration may be produced by the contact of feeble alkaline 

 solutions, which favour the liberation of the acids ; whilst, on the same 

 principle, a very small admixture of acid in the fluid with which the 

 seed is moistened, is found to produce a decided retardation. 



145. It is well known that Trees and Plants may be easily killed by 

 powerful electric shocks ; and that, when the charge is strong enough 

 (as is the case of a stroke of lightning), violent mechanical effects, as 

 the rending of trunks, or even the splitting and scattering of minute 

 fragments, are produced by it. But it has also been ascertained, that 

 charges which produce no perceptible influence of this kind, may destroy 

 the life of Plants ; though the effect is not always immediate. In par- 

 ticular it has been noticed, that slips and grafts are prevented from 

 taking root and budding. There can be little doubt that, in these in- 

 stances, a change is effected in the chemical state of the solids or fluids ; 

 although no structural alteration is perceptible. 



146. In regard to the influence of Electricity upon the Organic func- 

 tions of Animals, still less is certainly known ; but there is evidence that 

 it may act as a powerful stimulant in certain disordered states of them. 

 Thus in Amenorrhoea, a series of slight but rapidly-repeated electric 

 shocks will often bring on the catamenial flow ; and it is certain that 

 chronic tumours have been, dispersed, and dropsies relieved by the ex- 

 citement of the absorbent process, through similar agency. In fact, 

 there is strong reason to believe, that Electricity may be advantageously 



