378 INNERVATION. [CHAP. XI 



circuit. A deviation of the needle takes place immediately, which varies in 

 amount according to the number of segments which constitute the pile. 

 Matteucci has obtained a deviation of 15, 20, 30, 40, 60, etc., according to 

 the number of half-thighs, supposing the frogs employed to be equally lively ; 

 he obtained 3 or 4 with two elements, 6 or 8 with four elements, and 10 

 or 12 with six, and so on. These numbers are obtained, using distilled water 

 in the cavities ; but the deviation may be increased considerably if a few drops 

 of sulphuric acid be added to it, so that a pile of eight half-thighs, which gave 

 a deviation of 15 with distilled water, will cause 50 with the acid liquid. 

 "When the fluid was slightly saline or alkaline, the same number of elements 

 caused a deviation of 35. In all the trials the current had the same direction 

 that is, from the internal part of the muscle to its surface. 



The muscular current may be demonstrated with the muscles of other cold- 

 blooded and of warm-blooded animals. In all cases, it is necessary so to arrange 

 the elements of the pile, that the inner-surface of one segment shall be in 

 contact with the outer surface of the next, and that the inner surface of a 

 piece of muscle shall form one pole, and the outer surface of another piece 

 the opposite pole. 



The duration of the muscular current corresponds with that of contractility. 

 In cold-blooded animals, therefore, it is greatest. In mammalia and birds it 

 is very brief. Temperature has a considerable influence upon the intensity of 

 the current. If frogs are placed for some time in a very cold medium, piles 

 made from their muscles yield no evidence of electricity ; but, if the frogs are 

 placed in a warm medium for a short time after they have been taken from a 

 cold one, the current of electricity obtained from their muscles will be stronger 

 than that from a similar pile which had not been subjected to any change of 

 temperature. 



Any circumstances which enfeeble frogs, and derange their general nutrition, 

 will diminish the power of the muscles to generate electricity, as they also 

 impair the contractile force. Thus, Matteucci found the great heat of summer 

 to impair materially the development of electricity. We have found the same 

 result in frogs, which, having been kept crowded together in a small compass 

 during the month of December, became ill-nourished, with soft, flabby mus- 

 cles, full of moisture. The redder and more consistent the muscles are, as 

 Matteucci remarks, the more distinct will be the signs of electricity. 



The muscular current appears to be quite independent of the nervous 

 system. The segments of which the piles are formed are obviously beyond 

 the influence of the nervous centres ; and Matteucci has taken great pains to 

 remove from such segments all the larger nervous trunks and filaments dis- 

 tributed among the muscles without affecting the electrical current. And in 

 frogs, in which the lower part of the spinal cord had been destroyed by 

 burning, there was no evidence of impairment of the electric current in the 

 muscles of the lower extremities. 



Matteucci found that narcotic poisons, in moderate doses, had little or no 

 influence upon the muscular current. On one occasion, he found it slightly 

 increased in a frog to which a very small dose of opium had been given. In 

 very strong doses, such as to kill the animal, the muscular current is destroyed. 

 The influence of the narcotic gases upon the current is of no importance, with 

 the exception of sulphuretted hydrogen, which has the effect of materially 

 weakening its intensity. 



