CHAP. IX.] THE CONTRACTILE TISSUES. 317 



that muscular fibres consist of isotropous and anisotropous or doubly 

 refracting substance; that the latter is found in the broad dim band 

 which is made up of a series of sarcous elements; and that these 

 optically resemble uniaxal crystals the axes of which coincide with the 

 length of the fibre. By comparing the optical phenomena of muscles 

 and rock-crystal he assigned to muscle a place among positive double- 

 refracting bodies; and on purely physical grounds he assumed the 

 double-refracting powers to be due to the presence in the sarcous 

 elements of innumerable doubly-refracting particles, to which hypo- 

 thetical particles he ascribed the name of disdiaclasts (8/9, twice, and 

 St,aK\aa), I break in twain). 



The rest of the muscular fibre is isotropous in all meridians and 

 all positions; except Krause's membrane, which, like the sarcous 

 elements, is doubly refracting 1 . 



Of late years the scheme of striated muscle in Arthropoda, 

 mamS views anc ^ es P ec i a lly ^ n Insccta, has grown to be still more compli- 

 cated than in this description. With suitable powers, that 

 which has been called Krause's membrane becomes resolved into three narrow 

 bands, an intermediate and two accessory 2 . The intermediate band is 

 continuous, when in the fresh state, and sometimes double ; but broken into 

 granules when hardened. The accessory bands are usually more or less 

 granular. The intermediate band is double-refracting, as may best be seen 

 in hardened specimens of broad-banded muscles ; whereas double refraction 

 in the accessory bands is faint and uncertain. The diagram on page 314 

 should be consulted; it will be noticed that the double refraction of 

 Krause's membrane is omitted for the sake of simplicity. 



,,Y^TT*oi While the above general description includes all 



ouoaivision . . . V . 



of voluntary conditions of voluntary striated muscular tissues, 

 muscles into varieties are distinguished in the muscles of some 

 :edt animals: these are the pale and the red, of which the 

 unlikeness of colour persists after bleeding. In the former, transverse 

 striation is extremely regular and longitudinal striation merely 

 indicated : the recti, the vasti and the adductor magnus of the rabbit's 

 hind limb are instances. In the latter, or red variety, of which the 

 adductor brevis and the soleus are types, the transverse bands are 

 broken up by a well-marked longitudinal striation 3 . Still more 

 interesting physiological differences will be spoken of hereafter. 



1 See following note. 



2 Engelmann, Proces verbaal d. k. AJcad. van wetenschappen. Afdeel. NatuurJc. 

 No. 6, Dec. 1871 ; and No. 7, Jan. 1872. Referred to in a paper by the same author 

 ("Ueber die quergestreifte Muskelsubstanz ") in Pfliiger's Archiv f. d. ges. Physiol., 

 Vol. vn. , 1873, pp. 36, 42, 50. Unhappily the term 'strie intermediate ' has been applied 

 by Eanvier (Traite Technique d'Histologie, p. 481) to Hensen's disc. 



3 Eanvier, " De quelques faits relatifs a 1'Histologie et a la Physiologie des Muscles 

 strips." Arch. d. Physiol. norm, etpathol., 2nd Ser., Vol. i. p. 5, 1874. E. Meyer, "TJeber 

 rothe und blasse quergestreifte Muskeln." Arch. f. Anat. Physiol. u. wiss. Med. 

 (Eeichert und du Bois-Eeymond), 1875, p. 217. W. Krause seems to have been the 

 first to notice the distinction of colour in red and pale muscles (Anatomie des Kaninchens, 



