chap, ix.] STRIPED MUSCULAR TISSUE. 



for the blood when, during a sudden maximal contrac- 

 tion, it is pressed out from some of the capillaries. 



83. Each muscular fibre during contraction be- 

 comes shorter and thicker. In the living uninjured 

 muscular fibres, spontaneously or after the application 

 of a stimulus, a contraction starts at one point and 

 passes over the whole muscular fibre like a wave 

 contraction wavethe progress of which is noticeable 

 by the thickening, gradually and rapidly, shifting along 

 the fibre, the part behind resuming its previous diameter. 



84. When looked at in the fresh state, or after the 

 action of certain re-agents, the muscular fibre shows the 

 following parts 



(Fig. 40) : (1) a 

 transparent ho- 

 mogeneous deli- 

 cate elastic 

 sheath, the sar- 

 colemma ; (2) 

 dark delicate 

 lines stretching 

 across the fibre 

 at regular inter- 

 vals, so as to 

 sub-divide the 

 space within 

 the sarcolemma 

 into uniform 

 transverse com- 

 partments, the 

 muscular com- 

 partments of 

 Krause. These 

 dark lines are 

 the membranes 

 of Krause. Un- 

 der a high power they seem permeated or broken up by 



- a 



Fig. 40. Striped Muscular Fibres of the Water- 

 Beetle (Hydrophilus). 



a, Sarcolerama ; &, Krause's mcrahrane. The sarcous 

 elements are well seen. In A the oblong nuclei of 

 the muscle-corpuscles are shown. In B the s;m-<>- 

 leniraa has become unnaturally raised from the mus- 

 cular contents. The contract ilt> discs arc well shown ; 

 so also are the sareous elements. (Atlas.) 



