74 MUSCULAR TISSUE. 



bedded at various distances, and in cross sections they appear 

 thicker at the level of the nuclei. In an optical longitudinal 

 section, in which a lamina is seen in its whole length, it is ob- 

 served to be usually curved. In a transverse section it is also 

 often curved. We therefore conclude that these lamellae are 

 composed of placoid cells, each of which corresponds to a nu- 

 cleus, and constitutes a muscle-corpuscle, the limits of which 

 are indicated by the markings often seen between neighboring 

 nuclei. In Hydropliilus, muscular fibres are also met with, in 

 which the lamellae are replaced by cylinders. 



In the individual muscular fibres of the tongue of the frog, 

 obtained by taking a snip from that organ near the surface, 

 and covering it at once with serum, chains of oblong nuclei, or 

 large groups of nuclei without definite arrangement, are to be 

 found here and there. In the latter case, the nuclei are not all 

 oblong ; some of them are constricted and possess knobs. In 

 sections of tongue stained in gold, it is seen that these chains 

 and groups of nuclei are embedded in granular protoplasm, 

 which is continuous with the granular lamellae above described. 

 These bodies are therefore to be regarded as enlarged, many- 

 nucleated muscle-corpuscles. 



Tendinous Insertions. The transition from muscle to 

 tendon takes place in two ways : In one the transverse striae 

 cease, the whole muscular fibre passing into a tendinous bundle 

 of the same size, consisting of parallel wavy fibres. In the 

 other, the muscular fibre tapers to a blunt point, the sarco- 

 lemma extending beyond it as a thread-like structure of vary- 

 ing thickness, resembling, and becoming continuous with, a 

 slender bundle of connective tissue. Oblong cellular structures 

 may be seen in this fibre. The first form may be very easily 

 and completely demonstrated in a teased preparation in serum 

 or saline solution, in the muscular layer which extends, in 

 Hydrophilus, from the trunk to the first joint of the extremi- 

 ties, or in a similar preparation of the thoracic cutaneous 

 muscle of the frog. In the latter case, care will be necessary 

 to remove the tendinous insertions along with the muscle, and 

 to spread out the whole in serum or saline solution before 

 covering it. The second form can be studied in fresh teased 

 preparations of the muscles of the limbs of small mammalia, 

 or of the muscles of the larynx; but more easily in very thin 

 sections of the tongue of man or of mammalia, especially in 

 those fibres which radiate upwards towards the dorsal mucous 

 membrane. In sections of tongue hardened in chromic acid, 

 which are made across the long axis of the organ, bundles of 

 fibres are seen to pass upwards between the transverse^ cut 

 bundles of the longitudinalis linguse. Of these bundles it is 

 seen that certain of the muscular fibres stop short, the sarco- 

 lemma being prolonged into a thread, as above described. The 



