210 E. A. Schäfer, 



nor can it be said that we perceive the clear interval between that 

 element and Krause's membrane. It is true there is a bright band on 

 either side of Krause's membrane in the fresh muscle (Fig. 25 B) which 

 has usually been taken to represent the clear interval of the alcohol 

 fixed muscle. But the junction between the two, in place of being 

 sharply marked, as in the alcohol muscle, usually shows a gradation 

 of shading, and the bright band itself has every appearance of being 

 due to or at least increased by the effect of light reflected from a 

 plane surface such as that of Krause's membrane. This is certainly 

 the case in the majority of fibres which are not greatly stretched. In 

 those which happen to be much stretched, the clear interval may be 

 longer, and sharply marked off from the middle part of the segment 

 as in the alcohol muscle (Fig. 25 A). I have but rarely seen this myself, but 

 it has been described even in the fresh muscle by good observers. The 

 difference in appearance in the two conditions of the muscle may be 

 explained by supposing that the junction between the clear interval 

 and the sarcous element is in the more common condition (with ab- 

 sence of stretching) obscured by the light reflexion which occurs from 

 Krause's membrane, but that in the other condition (the stretched 

 muscle) this junction has become shifted beyond the limits of the 

 bright effect produced by reflexion and has therefore become visible. 

 In the acid muscle, after a short time, no distinction into sarcous 

 elements and clear intervals is seen: the whole segment between two 

 membranes of Krause is homogeneous in appearance. Probably this 

 is due to a dissolving of the sarcous elements by the acid. The same 

 result may be got in an alcohol preparation which is treated with 

 acid, if the alcohol have not acted too long upon the muscle, and it 

 is also characteristic of the ordinary gold preparations, in which 

 however, in consequence of the prolonged treatment with acid the 

 membranes of Krause and the envelope of the muscle column have 

 also disappeared. On the other hand, after prolonged treatment with 

 alcohol, and an after-treatment of gold, as in Rollett's method, the 

 sarcous elements become the most resisting portions of the muscle- 

 column and may, as we have seen, be set free after all the rest has 

 become dissolved. 



