Page:The American Cyclopædia (1879) Volume I.djvu/551

 ANIMAL ELECTRICITY 519 succeeded in obtaining a notable deflection of the needle. Unfortunately for the progress of science, Nobili admitted that the cur- rent formed in muscles was due to a differ- ence of temperature between the nerves and the muscles. Nevertheless, he left to his suc- cessors some facts of great importance, the mast interesting of which is that when the legs of several frogs are disposed in such a way that the nerves of one touch the muscles of an- other, this kind of pile increases in power with the number of legs. To Prof. Carlo Matteucci belongs the merit of having positively proved the production of galvanic currents in muscles. His researches, those of Du Bois-Reymond, of Donn6, of Baxter, of Brown-Sequard, of Eck- ard, and others, have established beyond doubt that a production of electricity is constantly going on in all the tissues of the living animal economy. The following facts, among others, have been well demonstrated: 1. When the electrodes or conductors of a galvanometer are applied one on one surface, and the other on another surface, of the animal body, a current takes place which moves the needle of the in- strument. Thus Donn6 found a current be- tween the skin and most of the internal mem- branes ; thus Matteucci ascertained that there are different electrical states in the liver and the stomach ; and thus also Baxter found a current between the internal surface of an in- testinal vein and any part of the mucous mem- brane of the bowels. 2. There are electrical currents in muscles and nerves, as we will show hereafter. 3. All the organs of the body yield electrical currents when they have been divided, and when their normal surface and the surface of the section are in communica- tion with the electrodes of a galvanometer. No one has been more successful than Du Bois- Reymond in experimenting upon the production of galvanic or electrical currents in the various parts of the body. He owes his success in a great measure to his galvanometer, which ad- mirable instrument, made by himself, is so sen- sitive that the exceedingly weak current from two parts of the skin, even very near each other, is felt by it. The wire wound upon the frame of this apparatus is 5,584 yards or more than 3 miles long; it forms 24,160 coils around the frame. However, it is not necessary to employ such a powerful instrument to prove the existence of animal electricity, and the or- dinary galvanometers may answer the purpose. Before the researches of Du Bois-Reymond it was admitted that there were two kinds of muscular currents, one belonging to divided muscles and the other to undivided muscles. The first had been very well observed by Mat- teucci, who ascertained that it is constantly directed from the interior of the muscles to its surface. It exists in the muscles of all the animals which have been examined, and Brown- i SSquard has found it in man. As to the other ! current, that of undivided muscles, it is what i Nobili called the proper current of the frog, i Du Bois-Reymond found that this current ex- ists also in the higher animals, and that its direction varies extremely according to many circumstances. In the limb of the frog this current is directed from the tendon of the prin- cipal muscles to their surface. If in certain animals the current seems to be weak, although it may be in reality strong, it is because in some muscles the tendon is placed at one ex- tremity and in others at the other, and that sometimes there are two tendons. The gal- vanic current of muscles gradually diminishes after the death of animals, or after the separa- tion of the muscles from the living body. Ac- cording to the researches of Du Bois-Reymond, and numerous experiments made by Brown- Sequard, the laws regulating the diminution and the disposition of the muscular current are the same as those of muscular irritability. Between these two physiologists, however, there is this difference, that Du Bois-Reymond thinks that the cessation of the current takes place at the time a supposed coagulation of the fibrinous liquid of the muscles occurs, producing the so-called cadaveric rigidity; while Brown-Sequard has shown that there is no such thing as this coagulation where cadaveric rigidity supervenes. The latter physiologist has discovered that the muscular current, after having completely disappeared (cadaveric rigidity being fully established), may be reproduced, together with the mus- cular irritability, when an injection of blood charged with oxygen is made into the arteries of a limb. This experiment he has per- formed not only on animals, but on the limbs of guillotined men. He found that the more oxygen there is in the blood employed, the quicker the muscular current and irrita- bility return. This fact, with many others dis- covered by Matteucci and Du Bois-Reymond, shows that the production of the current de- pends on the nutrition of the muscles, and par- ticularly on the oxidation of their tissues. Prof. Matteucci published many facts to prove that the muscular current is independent of the nervous system ; but his experiments are all open to objections. More decisive researches have been made by Brown-Sequard, who has ascertained that in muscles whose nerves have completely and definitively lost their vital prop- erties, currents not only exist during life, but may be reproduced by the influence of injec- tions of oxygenated blood when they have dis- appeared after death. Du Bois-Reymond has established as a law that every point in the natural or artificial longitudinal surface of a muscle is positive in relation to every part of its transverse surface, whether natural or arti- ficial ; and as the tendons, which are conduc- tors, are in communication with the natural transverse surface, it follows that they are negative as regards this surface. This law sig- nifies that the longitudinal surface of a muscle acts like the positive pole of a pile or galvanic battery, while the transverse surface acts like