462 PHYSICAL AND CHEMICAL PROPERTIES OF MUSCLE. 



substance, while Gscheidlen also observed that the finest terminal fibrils, one of which goes to 

 each muscular fibre, ran along the margins of the latter (fig. 314). The course of these fibrils 

 can only be traced after the action of gold chloride. [Ranvier has traced their terminations in 

 the stomach of the leech. ] 



Nerves of Tendon. Within the tendons of the frog, there is a plexus of medullated nerve- 

 fibres, from which brush-like divided fibres proceed, which ultimately end with a point in 

 nucleated plates, the nerve-flakes of Rollett. According to Sachs, bodies like end-bulbs occur 

 in tendons, while Rauber found Vater's corpuscles in their sheaths ; Golgi found, in addition, 

 spindle-shaped terminal corpuscles, which he regards as a specific apparatus for estimating 

 tension. 



293. PHYSICAL AND CHEMICAL PROPERTIES OF MUSCLE. 1. 



The consistence of the sarcous substance is the same as that of living protoplasm, 

 e.g., of lymph-cells ; it is semi-solid, i.e., it is not fluid to such a degree as to flow 

 like a fluid, nor is it so solid that, when its parts are separated, these parts are 

 unable to come together to form a continuous whole. The consistence may be 

 compared to a jelly at the moment when it is dissolved (e.g., by heat). The power 

 of imbibition is increased in a contracted muscle (Ranke). 



Proofs. The following facts corroborate the view expressed above : (a) The analogy between 

 the function of the sarcous substance and the contractile protoplasm of cells ( 9). (b) The 

 so-called Porret's phenomenon, which consists in this, that when a galvanic current is conducted 

 through the living, fresh, sarcous substance, the contents of the muscular fibre exhibit a stream- 

 ing movement from the positive to the negative pole (as in all other fluids), so that the fibre 

 swells at the negative pole (Kiihne). (c) By the fact that wave-movements have been observed 

 to pass along the muscular fibre, (d) Direct observation has shown that a small parasitic round 

 worm (Myoryctes Weismanni) moved freely in the sarcous substance within the sarcolemma, 

 while the semi-solid mass closed up in the tract behind it (Kiihne, Eberth). 



2. Polarised Light. The contractile substance doubly refracts light, and is said to be aniso- 

 tropous, while the ground substance causes single refraction, and is isotropous. According 

 to Briicke, muscle behaves like a doubly refractive, positively uniaxial body, whose optical axis 

 lies in the long axis of the fibre. When a muscular fibre is examined under the polarisation 

 microscope, the doubly refractive substance is recognised by its appearing bright in the dark 

 field of the microscope when the Nicols are crossed ( 297). During contraction of the mus- 

 cular fibre, the contractile part of the fibre becomes narrower, and at the same time broader, 

 whilst the optical constants do not thereby undergo any change. Hence, Briicke concludes 

 that the contractile discs are not simple bodies like crystals, but must consist of a whole series 

 of small, doubly refractive elements arranged in groups, which change their position during 

 contraction and relaxation. These small elements Briicke called disdiaclasts. According to 

 Schipiloff, Danielewsky, and 0. Nasse, the contractile anisotropous substance consists of myosin, 

 which occurs in a crystalline condition and represents the disdiaclasts. According to Engel- 

 mann, however, all contractile elements are doubly refractive, and the direction of contraction 

 always coincides with the optical axis. 



The investigations of v. Ebner have shown that during the process of growth of the tissue, 

 tension is produced the tension of bodies subjected to imbibition which results in double 

 refraction, and so gives rise to the condition called anisotropous. During a sustained con- 

 traction, the index of refraction of the muscular fibre increases (Exner). 



[Reaction. If a transverse section of a living excised muscle be pressed upon a strip of blue 

 litmus paper, the latter may assume a reddish tinge, and if upon a red litmus paper the latter 

 may assume a bluish tinge, but it will not alter violet litmus paper. This is the ampho- 

 chromatic or amphoteric reaction, indicating that the muscle, is neutral. It may, however, 

 give only an alkaline reaction. A living muscle plunged into boiling water still retains its 

 neutral or alkaline reaction ; but a muscle, which has been tetanised, or is in rigor mortis, is 

 decidedly acid.] 



The chemical composition of muscle undergoes a great change after death, 

 owing to the spontaneous coagulation of a proteid within the muscular fibres. As 

 frog's muscles may be frozen and thawed, and still remain contractile, they 

 cannot, therefore, be greatly changed by the process of freezing. Kiihne bled 

 frogs, cooled their muscles to 10 or 7 C, pounding them in an iced mortar, and 

 expressed their juice through linen. The juice so expressed, when filtered in the 

 cold, forms a neutral, or alkaline, slightly yellowish, opalescent fluid, the so-called 

 " muscle-plasma." Like blood-plasma, it coagulates spontaneously ; at first it is 

 like a uniform soft jelly, but soon becomes opaque ; doubly refractive fibres and 



