236 The Microscope. 



Fig. 17. — An intramuscular end of a fiber from the latissimus 

 of a house mouse in which the branches are long and give off 

 secondary branches. This form of ending is rare. 



Fig. 18. — An intramuscular branched end of a fiber from the 

 obliquus abdominis of a house mouse. This end is rather more 

 abrupt than those usually found. Dissociated in caustic potash. 



Figs. 19-21. — Transections selected from serial sections of the 

 vashis externus of a house mouse, to show the number, form and 

 relation of the fibers in a fascicule (see Part II) at different points, 

 c, Capillary, x Indicates the same fiber in each section. Fig. 19 is 

 of a section about 1 mm. from the tendinous end of the muscle. It 

 consists of six fibers, which show well the variety of shape. Fig. 20. 

 A transection of the same fascicule at about one- fourth the length of 

 the muscle from that shown in Fig. 19. The fascicule has increased 

 in size by joining another, and is composed of nineteen fibers. Fig. 

 21. A transection of the same fascicule not far from the middle of 

 the muscle. It has twenty -seven fibers, occupying about the same 

 space as the nineteen of Fig. 20; most of the fibres ai-e smaller, and 

 some are very small. The latter are transections of tapering ends of 

 fibers from the opposite tendon. 



Fig. 22. — Transection of part of another fascicule from the 

 same muscle at about the middle of its length. This gives an excel- 

 lent idea of an appearance common in the middle of this muscle, and 

 compared with Figs. 19-20 shows the relative diameter of fibers in 

 the middle and near the tendon of this muscle. Figs. 19-22 are 

 from specimens hardened in alcohol. 



Fig. 23. — Part of a fiber from near the middle of the pectoralis 

 of a house mouse. For three millimeters of its length it has clefts 

 such as seen in the figure. The nuclei are arranged in rows extend- 

 ing from the ends of the clefts; many of them are appaiently divid- 

 ing, as at n, while some are very long. This fiber has a fine, tapering 

 end, about 5 mm. from the part shown in the figure. 



PLATE X. 



Magnification of Figs. 24-31, 260 diameters, of Figs. 32-34, 

 180 diameters. 



Figs. 24-27. — Fibers from the muscular coat of the cardiac end 

 of the oesophagus of the house mouse. The ends are marked t; 

 they are similar to those at the ends of the fibers in the tongue, 

 but their relations were not made out. Fig. 24. A fiber 2 mm. long 

 with both ends branched. Fig. 25. A branched end of unusual form, 

 especially in the arrangement of the branches. Fig. 26. The body 



