LIVING MUSCLE. 117 



solution of sulphurous acid (the liquor acidi slil- 

 phurosi of the Pharmacopoeia answers very well). 

 The muscle is placed for a week or more in a well- 

 stoppered hottle containing a considerable quantity 

 of the acid, and is kept in a warm chamber (like 

 that shown in Fig. 19), heated to about #0 or 40 

 Centigrade. This very much facilitates the process 

 of maceration, so that after the time stated a mere 

 gentle shaking of the bottle is sufficient to cause the 

 muscle to break up in great measure into its consti- 

 tuent fibres. Some of these may then be removed, 

 placed side by side in water or weak glycerine on a 

 slide, and covered, with the usual precautions to 

 obviate the pressure of the cover-glass. It will be 

 found that the muscular substance has acquired, in 

 consequence of the maceration, a granular aspect, 

 and that the usual structural appearances are for the 

 most part indistinct. But this mode of preparation 

 may be advantageously employed for the purposes of 

 measurement and comparison of size and form of 

 fibres from different regions of the body. 



Preparation 10. Examination of muscular 

 tissue in the living condition. Ultimate struc- 

 ture of a muscular fibre. The delicacy of the 

 structural elements of the striated muscular fibres 

 of the vertebrata, and the difficulty of maintaining 

 the fibres, when sufficiently isolated, in the living 

 condition, have baffled all attempts that have hitherto 

 been made to satisfactorily determine their ultimate 

 structure before it has become altered either by the 

 death of the tissue or the action of reagents. But 

 the muscular tissue of some of the in vertebra! a, 

 particularly of insects and Crustacea, bears an exact 

 resemblance to the transversely striped contractile 

 tissue of the higher animals, while at the same time 

 the appearances are better marked, and separated 

 portions of the muscle are readily prepared, and may 

 be examined by the highest powers of the microscope 

 whilst still living and freely contractile. 



The most convenient of these animals to employ 



