MUSCLE-TISSUE. 275 



jected to mechanical injuries or chemical re-agents, into transverse disks. The 

 cleavage of the fiber lengthwise gives us the fibrillae, while a transverse 

 cleavage gives the disks. By splitting the fibers in a longitudinal and trans- 

 verse direction, this investigator obtained innumerable small cylindrical or 

 square pieces, which he called the sarcous elements. He maintained with great 

 positiveness that the striations in the muscle-fiber are due to a difference in 

 the refracting power of the intermediate substance, and that the longitudinal 

 and transverse splitting are not essential properties of the muscle, but are due 

 to mechanical or chemical injuries. 



The next investigator who has thrown light on this subject was E. Briicke.* 

 This observer maintains that the sarcous elements are by no means invariable 

 and unchangeable formations in the living muscle, but that they are rows of 

 corpuscles, differently arranged at the moment of death. On examining the 

 fiber with polarized light, he came to the conclusion that the sarcous elements 

 are constructed of very small, invisible particles, which he named disdlaklasts. 

 Upon the grouping of these minute bodies, he believed, depended the varying 

 formation of the sarcous elements. Briicke argues that the rows of sarcous 

 elements are double refracting, while the spaces between them are only 

 simple refracting. As to the nature and consistence of these intermediate 

 layers he offers no opinion. 



C. Heitzmannt pointed out an interconnection of the sarcous elements, 

 both longitudinally and transversely, by means of delicate filaments of living 

 matter, in the same manner as the granules of bioplasson in the amoeba are 

 connected. My own observations point strongly to the correctness of this 

 assertion. 



The observations of the investigators now mentioned are the principal 

 sources of our knowledge of striped muscle. The later researches on this 

 subject made by Hen sen, W. Krause, W. Engelmann, Heppner, and Alb. 

 Schafer have added little to our knowledge, as these authors have ex- 

 plained the structure of striped muscle in a complicated manner, and far 

 differently from what we really see. Perhaps Cohnheim's discovery of the 

 peculiar fields in transverse sections of frozen muscle deserve a remark, as 

 they appear to have been formed by the process of freezing, as we shall see 

 later on. 



If we take from the lobster a minute piece of perfectly fresh muscular 

 tissue and transfer it, together with a drop of the blood of the animal, to a 

 glass slide, and cover it quickly with a thin cover-glass, we may see, with 

 moderate powers of the microscope, the fibers composing it, of a nearly 

 uniform breadth. These fibers are separated from each other by exceedingly 

 narrow light spaces or rims, which in some places contain a granular mass. 

 A number of fibers are kept together by a delicate fibrous tissue, in which are 

 held the vessels and nerves. These latter features are seen best in a trans- 

 verse section of the muscle. Within the fiber may be noticed two kinds of 

 substance ; one is opaque, of a dim luster ; the other is light, uncolored, not 

 shining. In many places the two substances alternate with each other in 

 such a way .as to form rows, running in the transverse direction of the fiber, or 

 we may sometimes observe that the opaque substance is distributed without 



* " Untersuchungen iiber den Bail 'd. Muskelfasern mit Hiilfe des polar. Lichtes." Denk- 

 schr. d. Wiener Akad. Bd. xv., 1857. 



t " Untersuchungen liber das Protoplasnia." Sitzungsber. d. Wiener Akad. d. Wissensch., 

 1873. 



