M USCLE-TISSUE. 



267 



external perimysium unites into tendinous septa, and these 

 unite to form the fasciae and aponeuroses. 



Each muscle-fiber, besides, is again inclosed by an extremely 

 delicate hyaline, elastic membrane, the sarcolemma, first de- 

 scribed by Th. Schwann, in 1839. This sheath has not yet been 

 found in the muscle of the heart. The sarcolemma is distinctly 



FIG. 11]. RECTUS MUSCLE OF THE EYEBALL OF MAN. 

 VERSE SECTION. CHROMIC ACID SPECIMEN. 



TRANS- 



PE, external perimysium, containing, besides fat-globules and capillary blood-vessels, 

 also an artery, A, and bundles of medullated nerves, N; PI, internal perimysium, ensheath- 

 ing the single muscle-fibers. F. Magnified 200 diameters. 



seen only in transverse sections of muscle-fibers, but it becomes 

 visible also in longitudinal fibers, when broken through, or 

 after treatment with dilute acids, which destroy the muscle- 

 tissue without attacking the sarcolemma. The sarcolemma 

 appears as an apparently structureless, extremely thin, cor- 

 rugated membrane, destitute of nuclei. (See Fig. 112.) 



The attachment of the muscle-fiber to tendinous or periostea! 

 tissue is by means of the internal perimysium, while the sarco- 

 lemma terminates around the blunt or sharp point of the muscle- 

 fiber (C. Toldt). The tendons often exhibit rounded excavations r 

 in which rest the blunt ends of the muscle-fibers 5 thickened 

 elongations of the tendon penetrate to various depths between 

 the blunt extremities of the muscle-fibers. The perimysium,, 



