LIVING MUSCLE. 119 



may be seen in which the dotted line is absent, the 

 muscle rods not being enlarged at their extremities; 

 and these being placed end to end in the successive 

 series give an appearance of long, jointed fibrils ex- 

 tending in the direction of the length of the fibre. 

 In such fibres the cross-striped appearance is almost 

 entirely lost, for there are no intervening clear striae, 

 the appearance of which in the other fibres is proba- 

 bly due to the presence of the rows of strongly refract- 

 ing dots. 



That the bright appearance of the clear striae may be 

 produced by and dependent on the rows of minute globu- 

 lar ends of the muscle rods is shown by the following ex- 

 periment : A drop of water is placed on a slide, and a very 

 small drop of oil is transferred to it by a needle-point, 

 and is then thoroughly whipped up with it, so as to reduce 

 the oil to as minute globules as possible. The prepara- 

 tion is then covered and examined with the same magni- 

 fying power as was used for the water-beetle muscle. The 

 smallest of the oil-globules, like the dots in the muscle, 

 look like mere dark specks, and it will be noticed that 

 each is surrounded by a bright area, an effect always pro- 

 duced by highly refracting bodies when examined in a 

 less refracting medium. And if we imagine a number of 

 such little oil-specks to be placed in a row, there would 

 be a bright band on either side of the rows of dots in the 

 water-beetle's muscle. 



Contraction of muscle In the perfectly fresh pre- 

 parations of the insect's muscular tissue, spontaneous 

 waves of contraction may be seen passing from end to end 

 of many of the muscular fibres, and a general idea of the 

 phenomena which accompany the contraction, such as 

 thickening of the part of the fibre at the time the wave is 

 passing, and approximation of the cross-striae, may be 

 obtained. But the contraction proceeds too quickly for 

 the details of the process to be watched, and the fibres 

 are not sufficiently isolated; moreover, it is impossible to 

 s&y of the particular fibre under examination whether a 

 contractile wave is about to pass along it or not. 



Preparation 11. In order to get the fibres more 

 under command, the preparation must be made rather 

 differently. For the purpose of inducing the muscular 



