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 I 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 bemg 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 Ewchlanis tri- 
guetra and in the Euchlanis Hornemanni, which are not uncom- 
mon species ; the approach of the transverse strize 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 fibrille 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 fibrille 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 ustial 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 two 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 fibrille. 
The muscular fibres of the skate, treated in the same manner, 
afford easily-dissected and most characteristic examples of mus- 
cular fibrille. 
