292 



MANUAL OF HISTOLOGY. 



Fig. 286. Transverse section of the hu- 

 man biceps brachii. , muscle fibres; 

 6, section of a large vessel; c, a fat-cell 

 in a considerable connective-tissue in- 

 terstice ; d, section of a capillary vessel 

 in the thin septum of connective-tissue 

 between two muscle fibres ; e, nuclei of 

 the latter lying close to the sarcolemma. 



but as small round openings on their falling out. But, besides these, 



the sarcous elements appear, under low 

 magnifying power, more or less distinctly, 

 -* i n the form of extremely fine pale dots. 



167. 



We now come to a special modifica- 

 tion of striped muscular tissue, namely, 

 that formed of branching or reticulated 

 fibres. These are of frequent occurrence 

 in the lower animals, but are, as far as 

 we know, at present confined to but 

 limited portions of the human and mam- 

 malian body. 



For many years past the occurrence of 

 muscle fibres of this kind has been recog- 

 nised in the tongue of the frog. Here 

 they are seen dividing and subdividing at 

 acute angles. In the same organ of man they have since been found 

 by Biesiadecky and Herzig, as also by Rippmann, having been previously 

 observed in some of the mammalia. In the lips and snouts of many of 

 these animals the same variety of the tissue appears. 



On the other hand, the muscle of the human heart, and that of other 



vertebrates, shows with the greatest fre- 

 quency division of the fibres with anasto- 

 moses; thus the formation of regular 

 muscular networks. 



The muscle fibres of this organ (fig. 

 287) are smaller than elsewhere, and richer 

 likewise in fat molecules. Envelopes are 

 less apparent than on other striped fibres, 

 or are entirely absent. Finally, the trans- 

 verse striae appear with greater distinct- 

 ness, and the tendency to break up into 

 fibrillse is here considerable. 



The union of adjoining fibres (a, b) 

 is effected as a rule by short (c) and usually 

 slender branches, which leave the stem 

 now obliquely, now more transversely, so 

 that a regular network is produced, very 

 important in the mechanism of the 

 motions of the heart. 



According to Kodliker's statements, 

 each ramifying muscular element of the 

 heart corresponds to a stellate cell, and 

 the whole to a cellular network. Weismann, however, declares that his 

 investigations have led him to other conclusions. According to him, the 

 muscle bands consist (and it is easy to convince ourselves of the fact), in 

 fishes and amphibia, of simple elongated fusiform and sometimes branch- 

 ing cells, associated together. The same is the case in the embryos 

 of the higher vertebrates. 



In the latter, however, they become, later on, more closely united to 

 form the common mass of the band. But even here it is possible to 



Fig. 287. Muscle fibres from the heart, 

 after Schweigger-Seidcl. To the right 

 the boundaries of the cells and the 

 nuclei are to be seen. 



