234 



SPECIAL HISTOLOGY. 



Fig. 89. 



especially on the addition of water, acetic acid, and alkalies, 

 may at once be recognised as a perfectly structureless, trans- 

 parent, elastic, smooth membrane ; which 

 in man, as in the mammalia is distinguished 

 by its delicacy from the same tissue in the 

 lower Yertebrata, and particularly in the 

 naked Amphibia. The muscular or primitive 

 fibrils may, though not without difficulty, 

 be isolated, especially in muscles that have 

 j undergone slight maceration, or have been 

 boiled, or immersed in alcohol or chromic 

 acid. In general they are varicose, that is 

 to say, present more or less distinct enlarge- 

 ments, at intervals of 0-0004 — 0-001'" ; in 

 consequence of which arrangement, and 

 owing to the circumstance that the thicker 

 and thinner spaces, throughout the entire 

 thickuess of the fasciculus, are placed 

 regularly on the same level, the latter 

 for the most part appears to be marked 

 with delicate transverse bands. Occasionally, moreover, in 

 addition, a fine parallel striation is evident, or more rarely, 

 where the enlargements on the fibrils are less apparent or 

 quite imperceptible, simply a longitudinal striation. In adults, 

 the fibrils do not enclose any central space or canal (Jacquemin, 

 Skey, Yalentin), but, with the addition of a small quan- 

 tity of a connecting interstitial substance, constitute perfectly 

 compact fasciculi (fig. 90). On the inner side of the sarco- 

 lennna, numerous nuclei always exist, of a lenticular or fusi- 

 form shape, frequently with nucleoli, and from 0003 — 0-005"' 

 long. These nuclei are not placed with any regularity; some- 

 times two or more at the same level, or in rows, or alternately 

 one behind the other. Fatty, or yellowish pigment-granules, 

 also, frequently occur around the nuclei and between the fibrils, 

 chiefly, however, in muscular fibres, which are not in a perfectly 

 normal condition. 



The form of the muscular fasciculi is rounded-polygonal. 

 In thickness they vary from 0005 — 003'", or more; in the trunk 



Fig. 89. Primitive fibrils from a primitive fasciculus of theAxolotl (Siredon piri- 

 formis), x 600 diaiii.: 'i. a small fascicular composed of them ; b, an isolated fibril. 



