224 



Since writing the above note, I have observed a double 

 spiral arrangement of the striation in cardiac muscle fibres. 



DESCEIPTION OF PLATE Xll. 



Fig. 1. Voluntary Muscle Fibre from leg of Mouse, x about 

 500. The middle of the fibre is bent slightly downwards, and is 

 therefore at n different focus from adjacent parts. Avhich are 

 approximately surface views. Unstriped areas indicate blurred 

 focus. The gradual transition from "transverse" to ''crossed" 

 striation is clearly shown as the middle of the fibre (x) comes into 

 focus. 



Fig. 2. Muscle Fibre from leg of Mouse, xlOOO. The focus 

 is along the middle of the fibre, and clearly shoAvs crossing of 

 striations, being the optical effect of focussing the spirals in one 

 plane. 



Fig. 3. Human Muscle Fibre, well stretched, x920. The 

 fibre is observed at one single focus. The fibre has become 

 stretched to such an extent, that it is at times possible to obtain 

 &, slightly blurred image of top and bottom of fibre simultaneously ; 

 under these circumstances the complete doitWe spiral may be seen. 



Fig. 4. Portion of Muscle Fibre from Tongue of Dog, xl400. 

 The fibre has been considerably flattened, and shows bending down 

 of the striations at the sides of the fibre. Note especially, that 

 the blendings are in opposite directions. 



