CHANGES OCCURRING IN OLD MUSCULAR TISSUES. 231 



transverse markings continuous with the transverse 

 stria? of the muscle, fig. 1 c, PL VI, page 222. This deli- 

 cate material was no doubt contractile sarcous matter 

 imperfectly formed, which was gradually becoming 

 condensed and assuming the characters and pro- 

 perties of the adjacent contractile tissue with which 

 it was continuous ; and I was led to conclude that, 

 during the formation of the muscle, the oval mass of 

 bioplasm moved parallel with the fibre, giving rise to 

 the new tissue as it passed along, fig. 3, PL V, 

 page 217. Many appearances afterwards observed 

 confirmed this view. In the ordinary muscular fibres, 

 as those of the frog, which are well adapted for ob- 

 servation, the oval nuclei in different parts of the 

 fibre move upwards or downwards between several 

 fibrillse, and thus form new muscular tissue in every 

 part of the substance of these large elementary fibres. 



27O. Changes occurring in old. muscular tissues. 

 Fibrous degeneration of muscle. In old muscular 

 tissue the proportion of bioplasm to the formed 

 material is much reduced, and in some cases the 

 muscular fibre appears to be destitute of bioplasm 

 altogether. It nevertheless retains its contractile 

 power unimpaired. 



The proportion of tendon in connection with the 

 muscular tissue, as well as the thickness of the sarco- 

 lemma, and the quantity of connective tissue, gra- 

 dually increases as age advances ; and in old age much 

 of the muscular tissue is replaced by fibrous material. 

 The contractile material of the muscle has degene- 

 rated (?) into fibrous tissue. In this process the soft 

 contractile matter, which, as Kiihne has shown, is 

 fluid or semi-fluid, is absorbed, while an indistinctly 

 fibrous basis substance remains. A similar change 

 takes place after the contractility of muscle has for 

 some time been impaired, as results from many forms 

 of nerve paralysis ; and when the central nerve disease 

 progresses very slowly, a very great extent of mus- 



