FUNCTIONS OF MUSCULAR TISSUE. 329 



when all the Irritability has ceased, the muscles tear with a far less weight 

 than they were previously able, when galvanized, to draw. 1 



330. It appears from the researches of MM. Becquerel and Breschet, 3 that 

 Muscular contraction is attended with a disengagement of Heat. By careful 

 experiments, conducted with the aid of the " thermo-multiplier," they ascertained 

 that the temperature of a large muscle, such as the Biceps, uses as much as 1 

 (Fahr.) when it is thrown into vigorous contraction; and that repeated move- 

 ments of any one kind (as in the act of sawing) increases the temperature of the 

 muscles which execute them as much as 2. This development of Heat may 

 be attributed with probability to the chemical changes which take place in the 

 Muscular substance, when it is in a state of functional activity ( 311); or it 

 may be occasioned by the friction of its parts, upon one another; or we may 

 consider that, like Motion, it is a direct result of the metamorphosis of the force 

 which was previously operative in the vital actions of Development and Nutri- 

 tion. 3 It has been many times affirmed, but as frequently denied, that Elec- 

 tricity is developed during Muscular contraction. The recent researches of Prof. 

 Matteucci upon the cause of the phenomenon which he terms " induced contrac- 

 tion," have led him to an affirmative conclusion upon this important point. This 

 " induced contraction" takes place in the muscles of a prepared " galvanoscopic 

 frog," 4 when its nerve is laid upon the muscles of another frog, which are thrown 

 into contraction by electrical, mechanical, or any other stimulation of its nerves. 

 It is requisite that the nerve of the " galvanoscopic" frog should touch two dif- 

 ferent points of the contracting muscle or limb of the entire frog ; just as it is 

 necessary that two different points of the electrical apparatus of the Torpedo or 

 Grymnotus should be touched at once, in order to obtain manifestations of elec- 

 tricity. Prof. Matteucci has not succeeded in obtaining proof of electric dis- 

 turbance in contracting muscles, by any other means than the use of the " gal- 

 van oscopic" frog ; the most delicate galvanometer not affording unexceptionable 

 indications of it. 5 But he considers that the phenomena of "induced contrac- 



1 It has been inferred by M filler, from Schwann's experiments, that the power which 

 causes the contraction of a Muscle must be very different in its character from any of the 

 forces of attraction known to us ; since these all increase in energy as the attracted parts 

 approach each other, in the inverse ratio of the square of the distance ; so that the power 

 of a Muscle, if operated on by any of these, ought to increase, instead of regularly di- 

 minishing, with its degree of contraction. But it is' to be remembered that, as the obser- 

 vations of Mr. Bowman have clearly shown, there must be a considerable displacement of 

 the constituents of every fibre during contraction ($ 302) ; so that it is easy to understand 

 that, the greater the contraction, the more difficult must any further contraction become. 

 If, between a magnet and a piece of iron attracted by it, there were interposed a spongy 

 elastic tissue, the iron would cease to approach the magnet at a point, at which the attrac- 

 tion of the magnet would be balanced by the force needed to compress still further the in- 

 termediate substance. 



2 "Archives du Museum," torn. ii. p. 402. 



3 It is suggested by Nasse, that this elevation of the temperature of Muscles in action 

 is due to the increased afflux of arterial blood, which, according to him, is of higher tem- 

 perature than venous. But this position is by no means satisfactorily established. 



4 The " galvanoscopic frog," which has been continually employed by Prof. Matteucci 

 to test minute electrical disturbances which are not appreciable by a galvanometer, is 

 simply the leg of a recently-killed frog, with the crural nerve, dissected out of the body, 

 remaining in connection with it ; the leg being enclosed in a glass tube covered with an in- 

 sulating varnish, and the nerve being allowed to hang freely from its open end, when two 

 points of the nerve are brought into contact with any two substances in different electrical 

 states, the muscles which it supplies are thrown into contraction. 



5 On this account, Prof. Matteucci distrusts the results which have been obtained by M. 

 Du Bois Reymond ; who affirms that when the corresponding fingers of the two hands are 

 immersed in two vessels filled with salt water, into which are plunged two slips of platina 

 connected with the wires of a very delicate galvanometer, a very sensible deflection of the 

 needle, indicating a current from the hand to the shoulder, is produced by putting the 

 muscles of one arm in contraction against each other ; this deflection being considerably 



