THE HISTOLOGY OF THE STEIPED MUSCLE FIBRE, 229 



Transposition of the Bands. 



The effect known as " transposition" of the bands has been noticed 

 by many observers. On raising the objective what was previously the 

 bright band appears now darker than the dim band. 



This so-called transposition is seen in fibres prepared by the gold 

 method, better in fibres prepared with osmic acid ; diag. 6, u represents 

 a fibre at the upper focus. The light band in the position of Krause's 

 membrane appears very bright, and is bordered by a dark line at the 

 junction of the light and dim bands. On focussing about -0025 mm. 

 lower down (with Zeiss d obj.) the appearance seen in l is obtained. 

 The darkest part of the fibre is now in the centre of what was the 

 bright band, that is, in the position of Krause's membrane. Bordering 

 on this dark band, and separating it from the dim band, is a bright 

 zone. The dim band remains much the same as before, though by 

 contrast with the now dark Krause's membrane it may appear lighter. 



The bright haloes round the nodal dots of the network may be 

 compared with the similar effects observed whenever any highly 

 refractile particle, such as a micrococcus or minute oil globule, is 

 observed in a medium of lower refracting index. 



In the oil globule suspended in water similar and very definite 

 transposition effects are seen on altering the focus. If focussed low 

 it appears as a dark spot surrounded by a bright halo or border 

 (l, diag. 7). On raising the objective (about -0025 mm., Zeiss D) 

 the oil globule appears bright, surrounded by a dark border. 



The effect produced when a row of oil globules are seen side by 

 side is, at the lower focus (l), a bright band (formed by the coalesced 

 haloes), with a series of dark dots traversing it ; at the upper focus 

 (u) a narrower bright band, bordered by dark edges. The beads at 

 the nodes of the transverse network may be looked upon as refracting 

 and reflecting the light, in the same way as an oil globule in water, 

 and as causing the so-called "transposition" of the bands seen on 

 altering the focus. 



Identity of Network with Schafer's Muscle Bods. 

 We cannot but be struck by the resemblance of the appearances 

 brought out by gold staining with those described by Schafer 1 in the 

 living fibre as muscle rods. The two views differ, however, on two 



1 E. A. Schafer, "On the Minute Structure of the Leg Muscles of the "Water-beetle." 

 ' Phil. Trans.,' xii, 1873. 



