118 On the Structure of Voluntary Muscular Fibre. 



relaxation was as instantaneous as the contraction in that part 

 of the fibre which was the subject of it. 



The circulation of the blood was visibly accelerated after a 

 rapid series of contractions ; the blood seemed to be pressed out 

 of the vessels of the part undergoing contraction ; on relaxation 

 taking place the afflux was immediate. 



These observations were made at a time when 1 was much en- 

 gaged with other matters, and are consequently very imperfect. 

 I hope to be able to resume the inquiry during the ensuing 

 spring, when these interesting animals can be obtained in a pro- 

 per state for the examination. I believe this is the first obser- 

 vation of the contraction of a cross-striated muscle, so high in 

 the scale of being as the Batrachia. I may mention that Dr. 

 Allen Thomson repeated my experiments on the tadpole about 

 the same time and with similar results. 



Among the Rotifera I have observed very beautiful examples 

 of cross-striated muscle, more especially in the Euchlanis tri- 

 quetra and in the Euchlanis Hornemannij which are not uncom- 

 mon species ; the approach of the transverse striae is very marked. 

 The relaxed fibres are subject to a degree of zigzag flexure when 

 other muscles of the animal are in action. 



In conclusion, one word on the mode of displaying or separa- 

 ting fibrillse from the mass of a fibre, which is unquestionably a 

 very difficult operation. Mr. Lealand the optician seems to have 

 almost completely monopolized this branch of minute dissection, 

 as nearly the whole of the best preparations extant are from his 

 hands. I am not aware that he has yet made known his mode 

 of procedure to the public. 



If a muscular fibre of the salmon be used, it is in general not 

 very difficult to separate the fibrillse in water. Allowing it to 

 remain in moderately strong spirit for a short time, not only re- 

 moves the oil-globules from around the fibre, but greatly facili- 

 tates the dissection ; it may then be mounted in the usual way, 

 in spirit, or what perhaps answers better, in glycerine diluted 

 with about three times its bulk of water. 



The most characteristic specimens are obtained with greatest 

 ease from the frog, the size of the fibres rendering them very easy 

 to manipulate. Allow the leg of a frog stripped of integument to 

 remain in moderately strong spirit for about tv/o hours, then 

 commence the dissection with extremely fine needles set in long 

 handles. The largest fibres should be selected. After a few 

 trials the rudest operator can scarcely fail to separate the fibrillse. 



The muscular fibres of the skate, treated in the same manner, 

 affi)rd easily-dissected and most characteristic examples of mus- 

 cular fibrillae. 



