966 SUMMARY OF CURRENT RESEARCHES RELATING TO 



been often figured in the works even of recent histologists. If the 

 preparation be stained by any of the ordinary dyes, perhaps most 

 readily by picro-carmine, the border is in all cases very distinct, and 

 the regularly sinuous margin is unmistakable. Now, what is the 

 significance of the wavy outline ? It is, as will readily be understood, 

 that the fibre is ampullated, the wavy outline being but the optical 

 expression of such a figure. A muscular fibre is then not a smooth 

 cylinder, but is like the turned leg of a chair, or like the transversely 

 ribbed neck of a common water-bottle in shape. If the fibre be 

 broken up into fibrillae, which is very easy after maceration in 

 alcohol, these are seen to have just the same characters, indeed, a 

 small bundle of fibrils is most convenient for study. It may be well 

 to remark, that the ultimate fibrillre often show but little cross 

 markings, and appear almost smooth ; that is, however, only due to 

 their small size ; a good lens will bring out both points. . . . 



" The transverse stripings of the fibre are related to and corre- 

 spond with the inequalities of the surface. The little elevations at 

 the borders correspond, of course, to the little ridges, which run round 

 the fibre, while the dips at the borders are the optical expressions of 

 little valleys running between them. In the ordinary position, the 

 dark stripe marks the position of the ridge, and the light stripe lies 

 in the little valleys. 



" Then, again, Dobie's line (Krause's membrane), which is a faint 

 dark band in the very centre of the bright stripe, runs along the 

 bottom of the valleys, and Hensen's stripe in the centre of the dark 

 band, lies on the exact summit of the ridges. 



" This position of the stripes in a normal muscular fibre, is the 

 invariable rule, and the idea at once suggested itself, may not the 

 shape of the fibre itself cause the cross stripings ? 



" Any student of natural philosophy would at once affirm that a 

 structureless fibre of such a shape must be cross striped, and a glance 

 at the ribbed neck of the water-bottle on the table will elicit the 

 same answer from any one. 



" The question we must now determine is, are the appearances 

 seen in the fibre just the same, in all their details, as would be pro- 

 duced by a piece of glass, or any other homogeneous transparent 

 substance of the same shape ? 



" Before, however, entering into theoretical grounds, it may be as 

 well to give a full description of what is actually to be seen, for this 

 has not yet been stated. 



" With a structure of complicated figure, such as the one we are 

 considering, it is obvious that there is no one focus in which it may 

 be described. There is one pretty definite focus for a single si)eck 

 or thin film, but even when examining a simple cylinder, it is evident 

 that when the borders of it are clear and distinct, the upper surface 

 is slightly out of focus. We shall see, that in the case of the muscle, 

 although there is one position of the lens when the parts are very 

 distinctly seen, and in which they have mostly been described, yet 

 that on slightly altering the focus, the appearance is changed. These 

 changes we must carefully study. 



