72 MUSCULAR TISSUE. 



From all these facts we learn that the substance of a mus- 

 cular fibre consists, in the first place, of oblong prisms, i. e., 

 sarcous elements, with their axes parallel to its axis, and 

 formed of a material which refracts light strongly, is stained 

 strongly with silver, slightly with solution of chloride of gold, 

 and swells out in the fresh state on the addition of water ; and, 

 secondly, of a less refractive, transparent, interstitial substance, 

 occupying the remainder of the space ; which is not colored by 

 silver, but is intensely stained b.y chloride of gold, and dis- 

 appears in dilute acetic acid. This last reagent appears to 

 have the faculty of dissolving the interfibrillar part of the inter- 

 stitial substance, leaving the interstitial disks of the fibrils 

 almost intact. Similar facts are observed in muscles which are 

 subjected to the hardening influence of alcohol or chromic 

 acid. In sections of muscles so prepared, the fasciculi which 

 are cut transversely are seen to consist of disks, which are 

 either round or flattened against each other, and may be easily 

 stained in carmine or picric acid. In such disks the double 

 contoured section of the sarcolemma includes a number of small 

 roundish corpuscles, each of which, as may be seen in longitu- 

 dinal sections, is a fibril cut across. Muscular fibres, cut lon- 

 gitudinally, seem to consist merely of fibrils which are divided 

 bj r cross lines'into small long rods placed end to end. In sec- 

 tions of hardened tongue of the frog, it is very easy to obtain 

 isolated fibrils : thej" are also to be seen in teased preparations 

 of other muscles hardened in alcohol and chromic acid. 



The Sarcolemma. Each muscular fibre is invested in a 

 structureless hyaline membrane. To demonstrate it, the readiest 

 method is to add water to a fresh preparation of Hydrophilus, 

 or, better, frog muscle. After a short time the sarcolemma 

 separates in transparent bulgings with double contours. 

 Greater lengths of sarcolemma can be shown, by carefully 

 teasing fresh frog-muscle in salt solution. In such a prepara- 

 tion, fibres are always to be found, which, over a greater or 

 less extent, are no longer striated, but consist of a finely 

 granular mass. Continuing the observation, it is seen that the 

 parts of the fibre on either side of such a spot become con- 

 tracted, as indicated by the approximation of the transverse 

 stria?, and by the widening of the fibre. By virtue of this con- 

 traction, the granular muscular substance is torn asunder, the 

 sarcolemma being brought into view as a transparent tube. 

 Within this tube a greater or less number of granules are ob- 

 served in active molecular movement. As the disintegration 

 of the muscular substance progresses, an increasing quantity 

 of sarcolemma is brought into view. The broken up ends of 

 muscular substance are always irregular in form, presenting 

 numerous projections, none of which exhibit striation. By and 

 by fresh spots become the seat of the same change, so that the 



