MUSCLE-TISSUE. 277 



chromic acid, which is known to preserve and harden living matter, but not 

 to destroy its character or otherwise injure it. The results with the chromic 

 acid specimens were found to be the same as those observed in the fresh 

 muscle. Here, too, the alternating layers of sarcous elements and the inter- 

 stitial layers were plainly recognized. The rows of sarcous elements varied 

 greatly in breadth and form. If we tease a chromic acid specimen, we 

 obtain delicate longitudinal fibrillse, because we break the transverse connec- 

 tions the filaments of living matter which unite them together. Such an 

 artificially isolated fibrilla may appear beaded, as was asserted by Th. 

 Schwann, or it may exhibit a nearly uniform width throughout its entire 

 length, or the entire fibrilla may appear bright and homogeneous, and show 

 no trace of any difference in its optical properties in any part. This can be 

 explained by the fact that the sarcous elements within the muscle-fiber may 

 coalesce, or approach each other so closely that the intermediate light sub- 

 stance becomes invisible. We may explain the beaded condition of the 

 fibrilla either by saying that the living matter produces a solid square piece, 

 the sarcous element, which above and below is hollowed out and incloses 

 the interstitial liquid, or by saying that from both edges of the sarcous ele- 

 ment connecting filaments run to the neighboring sarcous element. 



In a longitudinal section of a muscle-fiber, we not infrequently meet with 

 oblong solid masses of a highly refracting nature, which are termed by the 

 authors, the nuclei. That such formations are present, not only on the sur- 

 face of the muscle-fiber, but also in its interior, is best demonstrated in trans- 

 verse sections, where, in the center of the fiber, we almost invariably observe 

 a more solid mass, with stellate offshoots which subdivide the muscle-fiber 

 into smaller fields. The presence of these large bioplasson masses within the 

 muscle-fiber has a close connection with the history of the development of the 

 muscle. Similar formations do, however, occur in the muscles of mammals. 

 I have especially observed globular or oblong bioplasson masses in the center 

 of the muscle-fiber of the ox. In making transverse sections, these masses 

 are very liable to fall out, or, perhaps, be drawn out by the razor, leaving an 

 empty space behind. This gives the incorrect impression that the muscle- 

 fiber is hollow in its center. 



Every muscle-fiber in mammals is known to be ensheathed in an extremely 

 delicate, firm, so-called elastic or hyaline membrane the sarcolemma. This 

 layer is present around the muscle-fibers of the lobster also. 



The statement of E. Briicke, which has gained general assent, that the 

 sarcous elements are possessed of a double refracting power, is, I am con- 

 vinced, incorrect ; at least, my own observations on the muscle of the lobster 

 with polarized light are not in accord with this view. I made a large number 

 of observations on specimens prepared in different ways, and also with perfectly 

 fresh specimens, moistened with a drop of the blood of the animal, and could 

 only obtain the phenomena of polarization in specimens of some thickness. 

 In every case when the specimen was very thin, and allowed the light to pass 

 through it freely, there was no evidence of polarization. W. Kuhne (1864) 

 failed to obtain polarization with the amoeba, and my observation with the 

 muscle-fiber of the lobster coincides with his. 



It is Doyere's and Kiihne's discovery that the motor nerves, which control 

 the action of the muscles, never enter the muscle fibers, but terminate on 

 their surface, generally in the form of hills, the so-called motor Mils. I have 

 observed similar formations in the muscle of the lobster, and, further, I have 



