144 FORCE TRANSFORMATION IN MUSCLE WORK. 



at the sides of the median membrane. As far as volume is 

 concerned, the contractile substance is in excess of the fluid in 

 a state of rest, whereas in the state of contraction the contrary 

 is the case " (Merkel). To this last sentence Engelmann does not 

 agree, and it is not easy to reconcile the observations of the 

 different experimenters in all details. Probably the above state- 

 ment of the homogeneity of the division during life refers to a 

 state of complete relaxation. Engelmann also states that during 

 contraction the isotropous substance becomes firmer and less 

 transparent, while the anisotropous becomes clearer and softer. 

 Schafer, on the other hand, asserts that the ground-substance 

 is anisotropous, while the rods are isotropous and in the state 

 of rest the whole fibre appears anisotropous, because the muscle- 

 rods are surrounded by the anisotropous ground-substance. 

 This last, he assumes, is comparable to a protoplasmic matrix, 

 which is the true contractile part, whereas the rods are elastic 

 structures, which serve to restore the fibre to its original length 

 after contraction has ceased (" Qu. Micro. Journal," April, 

 1874). So far are observers yet from being agreed as to the 

 physical process. 



As to the force requisite to produce these remarkable 

 changes, can we imagine any merely chemical change 

 in the semifluid single-refracting substance capable of 

 evolving and directing it ? We are here restricted to 

 the single-refracting substance, which is comparatively 

 small in quantity, for we know that the flesh prisms 

 are not consumed in the process, and how can we 

 imagine an evolution of force from chemical actions in 

 a formless fluid to be so directed as to change so exactly 

 the shape of those bodies imbedded in it ? The ques- 

 tion seems not worth discussion. The next theory is 

 that these movements are protoplasmic. This, of 

 course, involves the vitality of the fibres, which has 

 already been argued against, and besides that, I think 



