228 B. MELLAND. 



beaded disc occupying the position of "Krause's membrane." This 

 is shown in certain fibres in which the discs are not seen perfectly 

 edgeways but in perspective (fig. 6). The beaded disc at each 

 membrane of Krause is here seen to consist of a transverse or 

 horizontal network, united to the discs above and below by fine 

 thread-like lines. This method of gold staining, then, brings out a 

 network arranged in a manner represented diagrammatically in dia- 

 grams 1, 2, 3, and 4. 



This network differs chemically from the rest of the fibre, inasmuch 

 as it resists to a larger extent the action of acetic acid, and possesses 

 in a greater degree the power of reducing gold. 



It will be shown later, by other methods of preparation, that this 

 network differs again from the matrix in its physical properties. The 

 network is isotropous and highly refractile. The refractive power is 

 somewhat altered by gold staining, but certain optical effects are still 

 produced by the refractive action of the network upon light. These 

 optical effects can be more definitely seen in isolated portions of the 

 network than in the whole fibre. 



Optical Effects produced by the Network. 



Fig. 12 represents a small piece of the network isolated from the 

 rest of the fibre, consisting of nine or ten rows of dots and the 

 connecting longitudinal bars. There is a single layer only of network 

 and dots. This isolated piece seems to be a portion of sarcolemma 

 stripped off the fibre, along with the portion of network immediately 

 below the sarcolemma, and attached to it by each transverse network. 



When exactly focussed (fig. 14, l) each dot appears as a dark 

 granule surrounded by a bright halo. The blending of these haloes 

 causes a crenated bright transverse band. The effect of alternating 

 light and dim bands is thus obtained, the bright band being crossed 

 transversely by a row of dots, the dim band longitudinally by a series 

 of fine lines. 



On altering the focus (raising -0025 millimetre, about), the refractive 

 effects are to a certain extent transposed (fig. 14, u). The dots now 

 appear bright, surrounded by a dark border. By coalescence the 

 appearance of a narrow bright disc is produced, separated from the 

 dim disc at each side by a dark crenated line. 



Similar refractive effects and transposition on focussing are seen in 

 the discs isolated by transverse splitting of the fibre. 



