MUSCLE 



557 



d' 



admitted by all observers, there is a pretty general agreement 

 that in contraction a fluid does pass 

 from the clear ends of the sarcomeres 

 into the sarcous elements. According to 

 Rutherford, during contraction the in- 

 termediate segment first shortens, so 

 that the ends of Bowman's elements 

 come close up to Dobie's globules. 

 There is, apparently, no lateral bulging 

 of the intermediate segments while this 

 shortening is going on, so that the 

 fluid in them must enter Bowman's 

 elements. The Bowman's elements 

 begin to shorten a little later than the 

 intermediate segment. The easily- 

 stainable substance in them passes to 

 their ends, which swell and become 

 dimmer, while their shafts become 

 clear. The result of these changes is 

 that in the fully contracted fibril the 

 clear stripe occupies the middle of 

 what was the dim stripe in the uncon- 

 tracted fibril, and the dim stripe of the 

 contracted fibril is made up of ' the 

 swollen ends of Bowman's elements 

 with the Dobie's globules and other 

 tissue elements of the intermediate 

 segments' (Rutherford). This phe- 

 nomenon is known as the reversal of 

 the stripes. It is not really a reversal 



in the sense of being a bodily exchange 



r Al 11 f A i - i r .1 j. FIG. 165. CRAB'S MUSCLE 



of the whole of the material of the dim IN DIFFERENT STAGES 



and light stripes. Schafer has ex- F CONTRACTION (after 



, . ... RUTHERFORD). 



plained it as due to the squeezing of Three fibrilljfi are shown : 



sarcoplasm from between the sarcous >, complete relaxation ; t, com - 



ple'e contraction ; b-d 10 , sar- 

 elements into the position of the light cous elements ; d-d*, Dobie's 



stripe, when they bulge laterally in grar 

 contraction. This accumulation of sarcoplasm in the stripes 

 that were previously light makes them look darker in com- 

 parison with the true dim stripe. 







C/ 5 



c/8 



