STREAMLESS FRESH MUSCLES. 563 



surface, and two negative polar surfaces directed towards the transverse section. 

 Every fresh transverse section exposes new negative surfaces, and every artificial 

 longitudinal section new positive areas. 



This scheme explains the strong currents, when the + longitudinal surface is connected 

 with the - transverse sm*face, a current is obtained from the former to the latter, but it does 

 not explain the feeble currents. To explain their occurrence we must assume that, on the one 

 hand, the electro-motive force of the molecules is weakened with varying rapidity at unequal 

 distances from the equator; on the other, at unequal distances from the transverse section . 

 Then, of course, differences of electrical tension obtain between the stronger and the feebler 

 molecules. 



Parelectronomy. But the natural transverse section of a muscle, i.e., the end of the tendon, 

 is not negative, but more or less positive electrically. To explain this condition, du Bois- 

 Reymond assumes that on the end of the tendon there is a layer of electro-positive muscle- 

 substance. He supposes that each of the peripolar elements of muscle consists of two bipolar 

 elements, and that a layer of this half element lies at the end of the tendon, so that its positive 

 side is turned towards the free surface of the tendon. This layer he calls the ' ' parelectronomic 

 layer." It is never completely absent. Sometimes it is so marked as to make the end of the 

 tendon + in relation to the surface. Cauterisation destroys it. [It is supposed to be favoured 

 by cold.] 



The negative variation is explained by supposing that, during the action of a muscle and 

 nerve, the electro-motive force of all the molecules is diminished. During partial contraction 

 of a muscle, the contracted part assumes more the characters of an indifferent conductor, which 

 now becomes connected with the negative zone of the passive contents of the muscular fibres. 



The electrotonic currents beyond the electrodes in nerves must be explained. To explain the 

 electrotonic condition, it is assumed that the bipolar molecules are capable of rotation. The 

 polarising current acts upon the direction of the molecules, so that they turn their negative 

 surfaces towards the anode, and their positive surfaces to the cathode, whereby the molecules of 

 the intrapolar region have the arrangement of a Volta's pile. In the part of the nerve outside 

 the electrodes, the further removed it is, the less precisely are the molecules arranged. Hence, 

 the swing of the needle is less, the further the extrapolar portion is from the electrodes. 



II. Difference or Alteration Theory. The difference theory was proposed by 

 L. Hermann, and, according to him, the four following considerations are sufficient 

 to explain the occurrence of the galvanic phenomena in living tissues : (1) Proto- 

 plasm, by undergoing partial death in its continuity, whether by injury or by 

 (horny or mucous) metamorphosis, becomes negative towards the uninjured part. 

 (2) Protoplasm, by being partially excited in its continuity, becomes negative to 

 the uninjured part, (3) Protoplasm, when partially heated in its continuity, 

 becomes positive, and by cooling negative, to the unchanged part. (4) Proto- 

 plasm is strongly polarisable on its surface (muscle, nerve), the polarisation 

 constants diminishing with excitement and in the process of dying. 



Streamless Fresh Muscles. It seems that passive, uninjured, and absolutely 

 fresh nerves, and muscles, are completely devoid of a current, e.g., the heart 

 (Fngelmann), also the musculature of fishes while still covered by the skin. 



[According to Hermann, the currents obtained from muscle are due to injury of 

 the muscle-substance, whereby a difference of potential is set up, the injured part 

 being negative to the uninjured. In fact, it is impossible to isolate a muscle with- 

 out injuring it, owing to its connections. Frogs exhibit skin-currents after the 

 skin is destroyed ; the muscles still exhibit currents, but Hermann explains this by 

 the action of the irritant, used to destroy the skin, also affecting the muscle. In 

 fishes, however, there are no skin-currents, and if they be curarised, absolutely no 

 current is obtained from their uninjured muscles (Hermann). The heart also when 

 passive and uninjured gives no current, although it exhibits an action-current when 

 it contracts, and every injured part in it possesses a negative electrical potential 

 with reference to the rest.] 



L. Hermann also finds that the muscle-current is always developed after a time, which is very 

 short, when a new transverse section is made. [By means of his "Fall-rheotom," an arrange- 

 ment whereby a weight, covered with shagreen, injured a muscle, and at the same time, closed 

 and opened a galvanometer circuit, Hermann was able to show that the current demarcation- 

 current took a certain time to develop. Had it been pre-existent, as supposed by du Bois- 

 Reymond, this ought not to have been the case. ] 



