On the structure of cross-striated muscle. 205 



dealing with the question of the cross-striation of those muscles. The 

 staining is not in the least like that obtained by the ordinary gold 

 method in which the fresh preparation is used. For in the ordinary 

 method the inter-columnar substance or sarcoplasm is stained, but by 

 this method that substance for the most part remains colourless, and 

 the staining is confined to the muscle-columns. 



The muscle, or the insect with its cavities freely laid open, is 

 plunged in 93% alcohol, in which it remains 24 hours or more. It 

 is thence transferred to glycerine for several hours, and may then be 

 brought into l°/ chloride of gold solution, for a time varying from 

 5 minutes to half an hour or more; after which it is allowed to 

 undergo the ordinary reduction in formic acid. The striking feature 

 about muscles which are stained in this way, is the deep reddish 

 violet colouration of the principal part of the segment or sarcous 

 element, which, in properly stained fibres, is almost entirely lacking 

 in the rest of the segment. The appearance of transverse striation 

 thereby produced is most striking and is far sharper than in the fresh 

 condition or in any other mode of preparation. If the fibre is stretch- 

 ed or the sarcous elements are otherwise well separated from one 

 another, the inter-segmental membranes are well marked (Figs. 30, 

 35, 36); but if the sarcous elements are nearly approached to one 

 another, the inter-segmental membranes may not be visible (Fig. 28, a). 

 Although the sarcoplasm is not stained it is usually visible, but by 

 no means so conspicuously as in the ordinary gold preparation. In 

 different fibres considerable differences are observed, the ordinary mode 

 of staining tending to assert itself in some, and transitional effects 

 between the ordinay acid-gold images and the alcohol-gold images are 

 also observed. These differences depend, no doubt, upon the relative 

 time and degree to which the several fibres have been exposed to the 

 re-agents: by carefully overhauling a teased preparation made by this 

 method a large number of instructive pictures may be seen, even 

 within the limits of a single specimen. 



The above statements apply equally to the ordinary and to the 

 wing-muscles, but it is the latter the investigation of which gains 

 most by the employment of this method. Rollett has not himself 



