28 LIFE IN NATURE. 



muscles, and striped in those over which the will 

 has control. The stripes are transverse markings on 

 each fibre, as if it were composed of separate discs 

 arranged in lines (Figs. 3 and 4), and they afford a 



Fig. 3. 



Fig. 4. 



A fibre of striped, or "voluntary" muscle, showing its structure: magnified. 

 Fig. 3 shows the longitudinal, and Fig. 4 the transverse splitting. These and 

 the two following cuts are from Mr. Bowman's Paper in the Philosophical 

 Transactions for 1840. 



good means of examining the process of contraction. 

 When a portion of fresh muscle is made to contract, 

 under the microscope, by pricking or otherwise irri- 

 tating it, the markings, or stria3, approach each other, 

 the muscle diminishing in length and increasing in 

 thickness (Fig. 5). The action is gradually propa- 

 gated from the point of irritation to the adjacent 

 parts, with a creeping motion, subsiding in one part 



