286 



SPECIAL HISTOLOGY. 



the face is produced, at first by the voluntary contraction con- 

 sequent on the paralysis, upon the cessation of which it is 

 impossible that the previous symmetry of the features should 

 be restored, because the antagonist muscles on the opposite 

 side are paralysed, and their slight elastic force during life is 

 insufficient, simply upon the cessation of the contraction, to 

 restore the pristine position of the lips, angle of the mouth, &c. 

 An actual distortion, therefore, dependent upon persistent 

 muscular contraction, can only take place in consequence of 

 morbid conditions of the central organs. 



In the investigation of the muscles it is necessary that they 

 should be studied in the fresh state, and with the aid of 

 various reagents. The primitive fasciculi are most easily 

 isolated in muscles which have been boiled or immersed in 

 spirit, in which also, the transverse strise are for the most part 

 very well displayed, as is also the case after treatment with 

 corrosive sublimate or chromic acid. In the study of the 

 transverse strise, it is above all indispensable that the muscles 

 should be viewed in various degrees of extension and con- 

 traction (fig. 109). The former conditions, which are well 



Fig. 109. 



worth observation, are readily viewed, 

 if long slender muscles, such as the 

 hyoglossi of the Frog, &c, are examined 

 on a wooden stage having a central 

 opening filled in with glass. It will 

 then be seen, when no extension what- 

 ever is employed, that the transverse 

 striae are narrow (about 0-0004'") and 

 very closely approximated, and that 

 the fasciculus itself is broad ; whilst, 

 when it is extended to the utmost, the stripes are OOOOS'" 

 wide, and placed at the same distance apart, and that 

 the fasciculus is narrower. The contractions must be ob- 

 served either in fresh muscles still quivering, and kept moist 

 with serum, albumen, or vitreous humour ; or in the way pro- 

 posed by E.Weber, — and which consists in the galvanizing, by 



Fig. 109. A primitive fasciculus of a Frog's muscle in different degrees of exten- 

 sion, x 350 diam.: A, the fasciculus, stretched and slender, with broad distant 

 transverse striae ; B, the same not extended, broader, and with narrower, closely 

 approximated strife. 



