EXPLANATION OF THE PLATES. 



PLATE XLIL 



STRUCTURE OF MUSCLE. 



Fig. 1 . Muscular fibres and fibrilla3 of a voluntary muscle ; 

 in one of the fibres the fibrillae have given way, 

 thus allowing the sarcolemma to become apparent. 

 This figure, as well as most of the remaining figures 

 on this plate, are all magnified about 350 diameters. 



2. Voluntary muscular fibres acted upon by acetic acid, 



which brings clearly into view a number of granular 

 nuclei ; these nuclei are contained in the fibrillae, 

 many of which are unstriped, and two of which are 

 represented in the figure separately. 



3. This figure represents particulars in reference to 



muscular contraction ; in , a fibre is shown which 

 has been placed upon the stretch, the striae in it 

 are observed to be somewhat distant, b represents 

 the same fibre in a state of normal and ordinary 

 contraction, the diameter of the fibre is seen to be 

 much greater and the striae closer, c, the torn ex- 

 tremity of a fibre immersed in water prior to the 

 total extinction of its irritability, and which is ob- 

 served to be very greatly contracted ; the difference 

 of distance between the striae in the contracted 

 and uncontracted portions of the fibre is very re- 

 markable, d, a fibre which still retained its irrita- 

 bility immersed in water ; this has caused the fibre 

 to curl up, to become irregular and undulated ; the 

 transverse striae have disappeared, the longitudinal 

 markings at the same time being more apparent ; 

 in e the extremity only of the fibre has been im- 

 mersed in water. 



4. Shows the great variety in the size of the fibres of a 



muscle, the form of the extremities of the fibres, and 

 the mode of union between these and the tendon* 

 130 diameters. 



5. Transverse section of muscular fibres and intervening 



capillaries. 



