98 



NDOSMOSIS. 



digestion. It is well known that an effect of 

 lightning or the electric shock is to deprive 

 animated bodies very suddenly of their irrita- 

 bility ; and that thereby they are rendered more 

 readily disposed to pass into a state of disso- 

 lution than they would otherwise be ; in which 

 condition the digestive powers of the stomach 

 can be much more speedily and effectually 

 exerted on them. If any creature may seem 

 to require such a preparation of the food more 

 than another, it is the torpedo, the whole intes- 

 tinal canal of which is not more than half as 

 long as the stomach." 



These views receive some support from the 

 fact that the nerves of the stomach are derived 

 from those supplying the electrical organs ; and 

 perhaps also from the fact, reported by Dr. 

 Davy regarding a torpedo, in which, after it had 

 been frequently excited to give shocks, diges- 

 tion seemed to be completely arrested. 



The only conclusion to which, in the present 

 state of our knowledge, we can come on this 

 point is, that although the electrical organs form 

 a very efficient means of defence from their 

 enemies for the fishes which possess them, this 

 is not the only purpose they are intended to 

 serve ; what, however, their other uses are is at 

 present only matter of conjecture. 



There remains yet unentered upon a large 

 field of enquiry connected with the physiology 

 of those wonderful organs, which, we doubt 

 not, will yield to future ages very striking 

 examples of that nice and close adaptation of 

 means to ends which so clearly proves to us the 

 existence and continued exercise of Wisdom 

 Supreme, " upholding all things by the word of 

 his power," making the smallest of his works 

 " very good," and " to be thought upon." 



BIBLIOGRAPHY. Volta, Memorie sull' elettri- 

 cita animali, 1782. Galvani, Dell' uso e delP at- 

 tivita dell' arco conduttore nelle contrazioni del 

 moscoli. Bologna, 1794. Ejus. Memorie sulF 

 elettricita animale, Bologn. 1797. Fowler, Expe- 

 riments and Observations relative to the influence 

 called animal electricity. Lond. 1793. Aldini, 

 Essai Thcorique et experimental sur le Galvanisme, 

 et in Bulletin des sciences, an xi. No. 68. Pfaff* 

 Ueber thierische Elettricitat und Reizburkeit. 

 Leipzig, 1795. Humboldt, Versuche liber die ge- 

 reizte Muskel und Nervenfaser. Berlin, 1797. 

 Treviranus, Biologie. Tiedemann, Physiologic. 

 Mutter, Physiologic. Carus, Anat. Comp. French 

 ed. t. i. Lorenzini, Osservazioni interne alle tor- 

 pedini, Flor. 1678. Walsh, Phil. Trans. 1774. 

 Prmgle on the Torpedo, Lond. 1783. Ingenhousz, 

 Phil. Trans. 1775. Hunter, Phil. Trans, t. Jxiii. 

 et Ixv. Geoffroy Saint Hilaire, Ann. du Mus. t. i. 

 Humboldt, Recueil d'observ. de zoologie et d'anat. 

 romp. Knox, Edin. Journal of Science, 1824. 

 Todd, Phil. Trans. 1816. Davy, Phil. Trans. 1834. 

 Majendie and Desmoulins, Anat. des Systemes Nerv. 

 t. ii. Rtidolphi, Abhandl. der A cad. der Wissen- 

 Schaft in Berlin, 1820. Becquerel, Tiaite d'Elec- 

 Incite et Galvanism, t. iv. Par. 1836. 



(John Coldstream.) 



ENCEPHALON. In order to lay before 

 the reader a connected view of the Anatomy of 

 the Encephalon in conjunction with that of the 

 Medulla Spinalis, the Anatomy of both these 

 organs will be given under the article " NER- 

 VOUS CENTRES." 



ENDOSMOSIS, (ivbov, intus, uffpos, im- 

 pulsus). Accident having made me acquainted 

 with the fact that a small animal bladder, con- 

 taining an organic fluid, became considerably 

 distended by remaining for some time plunged 

 in water, and that the water even expelled the 

 thicker fluid contained within the bladder, when 

 there was a hole by which it could escape, I be- 

 thought me of the probable cause of this pheno- 

 menon, and soon came to the conclusion that it 

 depended on the difference of density between 

 the included or interior fluid, and the water or 

 exterior fluid. I found that the coeca of fowls 

 filled with milk, thin syrup, &c. and secured with 

 a ligature, became turgid and even excessively 

 distended when treated in the same way. I now 

 discovered that the fluids contained in the creca 

 permeated their coats, and were diffused in the 

 surrounding water. I saw, further, that two 

 opposite currents were established through the 

 parietes of the coeca; the first and stronger 

 formed by the exterior water flowing towards 

 the fluid contained in the cceca; the second 

 and weaker, by the thick included fluid flow- 

 ing towards the water. To the first of these 

 currents I gave the name of Endosmosis, and to 

 the second that of Exosmosis. These titles, I 

 must allow, are objectionable, and perhaps 

 badly chosen. The first conveys the idea of an 

 entrance and the second of an exit. Now, the 

 phenomenon, regarded in its proper point of 

 view, consists in a double permeation of fluids, 

 abstracted from any idea of entrance 'or exit. 

 Besides, the current of endosmosis, which, 

 etymologically speaking, expresses an in-going 

 current, may nevertheless be, experimentally 

 speaking, an out-going current ; this, for exam- 

 ple, happens when a hollow membranous organ, 

 containing water, comes to be placed in contact 

 exteriorly with a fluid more dense than water. 

 There is then a current of endosmosis which 

 goes out of the bladder, and a current of exos- 

 mosis which enters it. Thus facts are found in 

 contradiction to the terms, and these I should 

 not have hesitated to change, if their general 

 adoption did not render this change very diffi- 

 cult, and subject to great inconvenience. I have, 

 therefore, resolved to retain them, wishing it to 

 be understood by naturalists that no attention 

 is here paid to their etymological signification. 



To estimate the amount of endosmosis I 

 contrived an apparatus to which I gave the 

 name of endosmometer ; it consists of a small 

 bottle, the bottom of which is taken out, and 

 replaced by a piece of bladder. Into this bottle 

 I poursome dense fluid, and close the neck with 

 a cork, through which a glass tube, fixed upon 

 a graduated scale, is passed. I then plunge 

 the bottle, which I entitle the reservoir of the 

 endosmometer y into pure water, which, by en- 

 dosmosis, penetrates the bottle in various quan- 

 tities through the membrane closing its bottom. 

 The dense fluid in the bottle, increased in quan- 

 tity by this addition, rises in the tube fitted to 

 its neck, and the velocity of its ascent becomes 

 the measure of the velocity of the endosmosis. 



To measure the strength of endosmosis, I 

 have made use of an endosmometer in which 

 the tube was twice bent upon itself, the as- 



