406 



THE TISSUES. 



Fig. 257. 



induced by exercise is constantly seen. Mere increased size of the 

 original fibres may account for the effects of exercise, but there is 

 probably a growth of new fibres in the former case. Wedl asserts 

 that the number of fibrillae in the fibres is increased in pathological 

 hypertrophies; and in hypertrophied heart the fibres are of a tawny 

 or rusty-brown color, soft, and sometimes anastomosing, as seen in 



Fig. 257. It is also certain that 

 in hypertrophied muscles the con- 

 nective tissue between the fibres 

 sometimes becomes hypertrophied. 

 2. Atrophy of muscles is very 

 common, and occurs in old age, 

 from lead -poisoning, from paraly- 

 sis (especially of the tongue), and 

 from the development of cancer, 

 fibrous tumors, fat, &c., in the sub- 

 stance of the muscles. All causes 

 of general emaciation also pro- 

 duce it. 



In extreme old age, Kolliker 

 found the fibres small, sometimes 

 not more than -5^^ to T^CJS f an 

 inch in diameter; mostly without 

 striae, and with the fibrillae indis- 

 tinct; and often containing yellow- 

 ish or brown granules i^^^s of an inch in diameter, in large quan- 

 tity, and very many vesicular nuclei with nucleoli, together with a 

 clear fluid. 



In paralyzed muscles, Valentin found the transverse striae were 

 indistinct, or had actually disappeared, and could not be made to 

 appear by water, alcohol, &c.; while the longitudinal striae remained, 

 but resembled those of macerated muscle. 

 Subsequently the altered fibres disappeared 

 in part, and were partly replaced by fat. 



In a pectoralis major atrophied by cancer, 

 Kolliker noticed conditions similar to those 

 in old age. He also found cells in many of 

 the fibres exactly resembling the so-called 

 cancer-cells. Wedl states that in atrophy 

 some of the fibrillaa undergo absorption. 

 The fibre also manifests a diminished co- 

 hesion, and is easily lacerated ; the myo- 

 lemma being easily torn as well as the my- 

 oline within. (Fig. 258.) 



3. In fatty degeneration of muscles, ^ninute 

 fat-globules are developed within the myo- 

 lemma, in place of the fibrillae, which gra- 

 dually disappear. The fat-drops also accumulate between the fibres ; 



Muscular fibres in a hypertrophied heart. 

 a. A subdividing striated fibre, with dirty yel- 

 low pigment molecules in the myolemma. 6. 

 A slender dichotomous fibre, c. Anastomosing 

 fibre. d. Laminated, and e, smooth, colloid- 

 cell. Magnified 350 diameters. (Wedl.) 



258. 



Atrophy of striated muscular 

 fibre, a. A fibre torn across. 6. 

 Fibrillse hanging out. Magnified 

 350 diameters. (Wedl.) 



