234 The Microscope. 



Fig. 1. — A typical cylindrical fiber which extends from tendon 

 to tendon of the muscle. At the given magnification the diameter is 

 that of many fibers found in the mouse, shrew, bat and English 

 sparrow, while the length is that of one of the shortest fibers found 

 in the skin of the ear of the mouse, that is y\ mm. The ends, 

 though different, are of types frequently found; one is tapering, the 

 other truncate; both are made up of short finger-like processes. 

 Nuclei are in places scattered irregularly, in places arranged in rows, 

 and at the tendinous ends crowded together — and at n one shows 

 signs of division. 



Fig. 2. — A tapering fiber 7 mm. in length from a muscle 8 mm. 

 long from the brachium of a young sparrow. Most of the intra- 

 muscular ends occurred in the middle third of the muscle, but a few 

 fibers like this extended nearly its whole length. t, The tendinous 

 end has very fine processes and is smaller than the body of the 

 fiber, b. h Is two-thirds as large as b and is 1^ mm. from the intra- 

 muscu.lar end, i, which is a simple tapering end, a type common in 

 the sparrow. 



Fig. 3. — Part of a tapering fiber from the trapezius of a house 

 mouse. The muscle is 20 mm. long and this end occurs near the 

 middle, b, Body of the fiber; h, part of the fiber 1 mm. from the 

 intramuscular end, ^; both h and i have slight, bud-like, unstriated 

 processes. 



Fig. 4. — A tapering fiber from a muscle of the back of a gray 

 bat. The fiber is 6 mm. long, while the muscle is 7 mm. t, The 

 tendinous end has a great number of fine short prociesses, which 

 give it a fringed appearance. It is larger than the body of the fiber, 

 b. h Is I mm. from the end, i, which has near its tip a projecting 

 nucleus, giving the appearance of a process. 



Fig. 5. — A tapering fiber 1 1 mm. long, from a muscle 18 mm. 

 long, from the brachium of a young English sparrow. t, The 

 tendinous end is small but rapidly expands to 6, the body of the 

 fiber; h is 3 mm. from the intramuscular end, i, which is a simple 

 bifurcated form common in the English spaiTow, less frequent in 

 the other animals. 



Fig. 6. — A tapering fiber from the obliqims abdominis of a 

 house mouse. t, The tendinous end is of a type not uncommon in 

 this and some other muscles; a number of similar ones were found 

 in situ. b, The body of the fiber is smaller than t h Is smaller 

 than b and is 6 mm. from i, the bifurcated intramuscular end, a form 

 not common in the limb and trunk muscles of the mouse. 



