74 CONTRACTILE ELEMENTS. 



find that, in this case, the current is reversed or disappears) 

 much study has been given to this subject ; and, after speci- 

 fying the conditions of the current, it has been sought to 

 explain them by what is called the theory of peripolar-elec- 

 tric molecules. We will not, however, explain in detail this 

 theory, for it is probable that the study of these currents is not 

 of supreme importance in the physiology of the muscle, but 

 that they should be considered simply as the result of the 

 chemical phenomena of which the muscles are the seat, and 

 which are more or less active as the layers may be more or less 

 superficial. In fact, the shape of the pieces of muscle em- 

 ployed in experiments has great effect upon the direction of 

 the current ; a muscle may possess its normal electric cur- 

 rent, and yet have lost all its other properties ; thus, poisons 

 which kill the muscle have not always the same effect upon 

 its electro-motor power; finally, similar currents have been 

 observed in living tissue of various kinds, even in vegetables, 

 as, for instance, in pieces of the pulp of a potato. 



B. The muscle, under form No. 2. 



The muscle, in this state, only differs essentially in a change 

 of form from what it was in the preceding state : it* is shorter 

 and thicker ; a fusiform muscle becomes globular. The dif- 

 ference may, in general, be estimated at , that is, the muscle 

 under form No. 2, becomes shorter by f of its former length 

 under form No. 1. But its transverse dimensions increase in 

 exact proportion to the diminution of its longitudinal dimen- 

 sions, and there is, consequently, no change in its bulk. If 

 we place in a graduated vessel, full of water, a muscle of 

 form No. 1, and by any excitation cause it to pass into form 

 No. 2, we shall find no change in the level of the fluid. 

 Lately, however, Valentin has ascertained, by an extremely 

 minute process, that a muscle, in passing from the first to the 

 second form, increases in density in the ratio of TsW> ^ u ^ 

 this fraction represents such a slight diminution of bulk that 

 it seems quite unworthy of notice. 



The bulk remaining the same, we have then, in order to 

 make a comparative study of the muscles, under form No. 2, 

 only to consider it in the triple aspect of the properties 

 already studied in form No. 1 : its elasticity, chemical phenom- 

 ena, and electro-motor power. 



Elasticity. The muscle in form No. 2, when not pre- 

 vented from completely taking this form, is as soft and elastic 

 as in form No. 1. If it is then handled, it is found to be ex- 



