46 ELECTRO-PHYSIOLOGY CHAP. 



of W. Krause, that every muscle-column is composed of strata of 

 " muscle- cases," which in juxtaposition form the " muscle-com- 

 partments " of the entire fibre ; each muscle-case, bounded beneath 

 by (Z) the "basal membrane," contains, as well as fluid corre- 

 sponding with (<7), a " muscle-prism," represented like the Bowman 

 " discs " by the (Q h Q) system of stria?. Krause only takes account 

 of the fibrillated structure of the muscle-fibres, in so far as he 

 assumes the muscle-prism to consist of muscle-rods (Bowman's 

 " sarcous elements "), which, according to the description given 

 above, correspond with the segments of fibrils (Q li Q) only. The 

 untenability of this theory, according to which not fibrils, but 

 muscle-cases, are the elementary constituents of the muscle-fibre, 

 is obvious from the facts we have stated ; the breakdown into discs 

 within the segment (Q) in the acid reaction is very convincing- 

 evidence against it. Nor is there any better justification for the 

 muscle-elements of Merkel, which are each bounded by two (Z\ in 

 this case necessarily assumed to be divisible. This is not the place 

 to enter into the many other systems (including Biitschli's " cell 

 theory") that have been elaborated from time to time, in regard 

 to the much disputed finer, and finest, structures of striated 

 muscles. 



We have already had frequent occasion to refer to the optical 

 properties of muscle-fibrils, especially in striated muscle. Even 

 wiien examined in ordinary light the different segments of the 

 striated fibrils exhibit a very different refractibility ; it may 

 indeed be said, with reference to Eollett's system of indicating 

 the individual segments, that all the bands denoted by consonants 

 are more highly refracting, and also doubly refracting (anisotropous) 

 although in very different proportions. 



As was said above, the bands (Z) and (TV) appear much 

 darker than ($) with a certain (low) power of the microscope, 

 and it is owing to the strong refractibility of (Z) in particular 

 that it is easily recognised even in imperfect preparations. The 

 strife denoted by the vowels (J) and (E}, as well as (h}, are, on 

 the other hand, less refractile and singly-refracting (isotropous) ; 

 these, under conditions which make the bands denoted by con- 

 sonants appear dim, will be clear and inverted. The doubly- 

 refracting property of striated muscle-fibres was discovered by 

 Beck in 1839, but Briicke in 1857 was the first to examine it 

 minutely. 



