224 SPECIAL HISTOLOGY. 



numerous nuclei always exist, of a lenticular or fusiform shape, fre- 

 quently with nucleoli, and from 0-003-0-005 of a line long. These 

 nuclei are not placed with any regularity ; sometimes 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 thick- 

 ness they vary from 0-005-0-03 of a line, or more. In the trunk and 

 extremities they are invariably thicker (0-016-0-03 of a line) than on 

 the head, in which situation, especially in the facial muscles, they are 



Fig. 90. Fig. 91. 



C 



distinguished by the smallness of their fibres (0-005-0-016 of a line) ; 

 but, with respect to this, it is to be remarked that great differences not 

 unfrequently exist in one and the same muscle. From all that is known, 

 it would appear that there is no absolute difference in the size of the 

 muscular fibre in man and in woman, or between weak and robust indi- 

 viduals. On the other hand, it is not improbable that in one case one 

 extreme, and in a second the other, may prevail. The thickness of the 

 primitive fibrils, in man, amounts on the average to 0-0005 of a line; 

 their number, in one of the larger fasciculi, must reach several hundreds, 

 but is not accurately known. The distance between the transverse 

 striae varies usually from 0-0004 to 0-001 of a line. 



Various controversial opinions still prevail with respect to the consti- 

 tution of the muscular fibres. Several authors assert, or at all events 

 consider it probable, that the primitive fibrils are produced artificially. 



FiG. 90. Transverse section of some muscular fibres or primitive fasciculi from the 

 gaslrocnemius of man ; magnified 300 diameters : a, sareolemma and interstitial connective 

 tissue ; ft, transverse section of the muscular fibrils, with the interstitial substance. 



FiG. 91. Portion of a muscular fibre of man. treated with acetic acid, magnified 450 

 diameters: a, sareolemma; 6, a simple nucleus; c, double nucleus, surrounded with fatty 

 molecules. 



