MUSCULA R TIXS i /, . 



67 



another thin bridge joining the same granule to the next sarcous element, and so 

 on. When these fibrillse are collected together into columns, and the columns into 

 muscular fibres, the appearance mentioned above is produced. The sarcous ele- 

 ments, when arranged side by side and almost touching each other, with very 

 little sarcoplasm between them, represent the transverse disk. The bridges, being 

 much thinner than the sarcous element or the dark granules, have between each 

 other a much larger amount of sarcoplasm. and this gives to this part the trans- 

 parent appearance of the lateral disk. And. lastly, the granules joined edge to 

 edge in a row present the appearance of a membrane, which represents the inter- 

 mediate disk. 



On the muscular fibre, immediately beneath the sarcolemma. the sarcoplasm 



FIG. 4'). Portion of a medium-sized human muscular 

 fibre. Magnified nearly 800 diameters. B. Separated bun- 

 dles of fibrils, equally magnified, a. a. Larger, and 6. b, 

 smaller collections, c. Still smaller, d. d. The smallest 

 which could be detached. 



FIG. 4L Part of a striped muscular fibre 

 of the water-beetle, prepared with absolute 

 alcohol. Magnified 300 diameters. (Klein 

 and Noble Smith.) a. Sarcolemma. 6. 

 Membrane of Krause : owing to contrac- 

 tion during hardening, the sarcolemma 

 shows regular bulgings. At the side of 

 Krause's membrane is the transparent lat- 

 eral disk. Several nuclei of muscle-cor- 

 puscles are shown, and in them a minute 

 network. 



becomes here and there collected into small, plate-like masses. They contain oval 

 nuclei, and are termed muscle-corpuscles."' Finally, in the centre of each 

 sarcous element a transparent lighter band can sometimes be discerned ; this is 

 known as the me<li<tn <li*k of Hensen. and is due to the substance of the sarcous 

 elements being here thinner. 



This form of muscular fibre composes the whole of the voluntary muscles, all 

 the muscles of the ear. those of the larnyx, pharynx, tongue, the upper half of the 

 oesophagus, the heart, and the walls of the large veins at the point where they 

 open into it. The fibres of the heart, however, differ very remarkably from those 

 of other striped muscles. They are smaller by one-third, and their transverse 

 stria? are by no means so distinct. The fibres are made up of distinct quadran- 

 gular cells joined end to end (Fig. 42). Each cell contains a clear oval nucleus. 

 situated near the centre of the cell. The extremities of the cells have a tendency 

 to branch or divide, the subdivisions uniting with offsets from other cells, and 

 thus producing an anastomosis of the fibres (Fig. 42). The connective tissue 

 between the bundles of fibres is much less than in ordinary striped muscle, and 

 no sarcolemma has been proved to exist. 



The c<Ti')H<irifs of striped muscle are very abundant, and form a sort of rect- 

 angular network, the branches of which run longitudinally in the endomysium 

 between the muscular fibres, and are joined at short intervals by transverse 

 anastomosing branches. The larger vascular channels, arteries and veins, are 



