ANIMAL. 



137 



of infusory animals within its bosom. Many 

 tribes of insects shine in the dark. The phe- 

 nomenon is not certainly known to be mani- 

 fested by any of the class of reptiles, birds, or 

 mammalia. It appears to depend, in insects 

 particularly, on the presence of a peculiar 

 matter, secreted by their bodies and stored up 

 in particular points, which, under the influence 

 of a temperature elevated in a certain degree, 

 and the contact of atmospheric air, enters into 

 a kind of combustion during which light is 

 emitted. Is the phenomenon dependent on 

 one common cause in both vegetables and 

 animals, supposing that it does really occur 

 among the former? 



Electrical phenomena are extensively ex- 

 hibited by the objects composing the unor- 

 ganized and the organized world. In fact, 

 wherever there is composition and decompo- 

 sition going on, there are electrical phenomena 

 manifested. The action of the immense mass 

 of vegetables on the air, the evolution of oxygen 

 in the sunshine, and the formation of carbonic 

 acid during the dark, has even been supposed 

 by an ingenious natural philosopher of France 

 (Pouillet) to be the principal source of the 

 electricity of the atmosphere. 



Galvanic electricity is excited by the contact 

 of the different parts of which animal bodies 

 consist, particularly of the nerves and muscular 

 flesh ; the nerve of a frog's thigh exposed and 

 isolated, touched with a piece of quivering 

 flesh from the body of a bullock just slain, also 

 isolated, causes the muscles to which the nerve 

 is distributed to contract energetically (Hum- 

 boldt). The same phenomenon occurs when 

 different other parts and fluids, particularly the 

 blood, are used to form a chain. But the 

 electrical phenomena manifested by animals at 

 large, are weak when contrasted with those 

 exhibited by certain fishes provided with spe- 

 cial voltaic piles or galvanic batteries by which 

 they give at will, but not otherwise, electrical 

 shocks of such violence as to stun larger ani- 

 mals and even to deprive smaller ones of life. 

 This electricity of animals must be held as a 

 vital phenomenon ; several of them have in- 

 deed a peculiar apparatus for the preparation 

 of the shock, to speak of the phenomenon by 

 its effects, in our ignorance of its essence or 

 efficient cause, but this loses its power when 

 the nerves that are abundantly distributed to it 

 are divided. 



Electrical phenomena are not so obviously 

 displayed by any other tribe of animals as by 

 fishes ; but it has been rendered next to certain 

 that muscular contractions are uniformly accom- 

 panied by a kind of electrical discharge from 

 the nervous fibrils distributed to the special or- 

 gans of voluntary motion. 



Animals, from this brief review, appear to pos- 

 sess electrical capacities in a much higher de- 

 gree than vegetables, in which the phenomenon 

 is even explicable on ordinary chemical prin- 

 ciples, whilst among animals it is unquestion- 

 ably one of the effects of vitality. 



We have already indicated the existence of 

 two faculties among animals which become 



necessary or complemental to them as agents 

 entrusted with their preservation as individuals, 

 and their continuation as kinds ; these are 

 voluntary motion and sensation. But motion 

 in the abstract is a phenomenon of much more 

 extensive occurrence among organized beings 

 than the notion we form of the act as connected 

 with the existence of a muscular system. Mo- 

 tion is in fact a quality inherent in organized 

 beings ; they cannot be conceived as existing 

 without change, and change implies motion. 

 In most, or indeed in the whole of the actions 

 which we have glanced at as manifested by 

 them, we have supposed motion. The simplest 

 of all animals, the infusoria, move about in 

 many cases with great briskness ; the polypes, 

 composed of an uniform gelatinous mass, also 

 move in various directions ; the acalephs, with 

 a similar structure, rise from the bottom and 

 propel themselves through the waters of the 

 ocean by a succession of contractions of their 

 disc, of their tentacula, or of the fringe-like 

 or foliaceous bodies with which several orders 

 of the genus are provided. Many of the en- 

 tozoa too, whose bodies consist of a simple 

 gelatinous or mucous tissue, execute motions in 

 various senses. 



But it is not only as a whole that a body 

 endowed with life and organization possesses a 

 capacity of motion. Many of its parts, and 

 particularly the globules which enter as essen- 

 tial and integral parts of the fluids contained 

 in organized bodies, have inherent powers of 

 motion; the globules of the blood, for instance, 

 those of the spermatic fluid, and perhaps also 

 the germ included within the ova of the polype, 

 mollusc, &c., have all been observed in motion, 

 and the means by which it is accomplished 

 even demonstrated in many cases. But there 

 is nothing absolutely peculiar in such indivi- 

 dual instances, for we must need conceive 

 motion in the first constituent elements of all 

 organisms without exception, long before a 

 muscular, a cellular, a nervous, or any other 

 distinct system has existence.* 



Motion of all kinds, therefore, automatic as 

 well as that which is voluntary, must be held 

 as a quality inherent in organized or living 

 beings. The cause of this phenomenon, as of 

 so many others manifested in the world of or- 

 ganization, has been the subject of much dif- 

 ference of opinion and of much dispute among 

 physiologists, and many titles have been ima- 

 gined by which the agent or primary cause of 

 the act has been sought to be designated, or 

 the act itself to be explained. 



It is quite certain that the capacity to com- 

 mence and to continue the phenomena which 

 we designate as vital, or the motions which 

 constitute these phenomena, depends first on 

 a variety of external conditions, such as a 



* Such motion is indubitable. The organic glo- 

 bule has capacities of motion inherent in itself, 

 different from the motions of unorganized objects 

 in a state of extreme division, as is proved by the 

 motions of each kind of body being different, and 

 those of organized globules being interrupted by the 

 electric spark, or whatever destroys their vitality 

 acids, alkalis, poisons, &c. 



