364 Mr. J. B. Haycraft. Upon the Cause of [Feb. 3, 



very well tlie results of my own observations, which I find, are in 

 accordance with those of other observers. (See the " Handbuch der 

 Physiologie," by Dr. H. L. Hermann, 1879, p. 20.) The black part 

 of the diagram corresponds with the portion of the muscle which 

 singly refracts light (isotropous), while the light shaded parts cor- 

 respond with the anisotropous substance. 



This diagram does not, it will at once be seen, correspond with the 

 views held by Brucke, for the great mass of the light stripe, with 

 Dobie's line in the centre of it is anisotropous, the dark band, as with 

 Brucke, being anisotropous. The most recent view is, then, that 

 both the light and the dark stripes doubly refract light, but that 

 there are bands which lie between them and which are singly refract- 

 ing. The appearance which partially warrants such a conclusion 

 I have observed, but I shall endeavour to show hereafter how this 

 may most satisfactorily be explained. It will readily be seen how 

 Briicke's view, until quite recently accepted, would drive one to 

 the conclusion that the light and dark stripes represent two diffe- 

 rent structures alternating fi in the length of the fibre, and this is 

 corroborated by statements as to the action of staining agents on the 

 tissues. 



Muscle is readily stained by picric acid, but is but faintly 

 tinted by carmine, logwood, or eosine, although Ranvier, in his 

 " Traite Technique d'Histologie," states that he has obtained very 

 beautifully stained preparations of insects' muscle, when using 

 Bcehmer's solution of logwood. According to this observer, the dark 

 stripes as well as Dobie's lines are stained, while the rest of the fibre 

 remains colourless. Klein in his " Atlas of Histology " figures the 

 sarcous matter of the dark band clearly tinted, while that of the light 

 stripe is absolutely colourless. The statement will not be far wrong, 

 that everyone at the present time considers the dark and light stripes 

 as representing two different structures, distinct one from another in 

 their physical properties, for the dark stripe is spoken of as possess- 

 ing a higher refracting power than the light, and chemically, for their 

 compositions have alrea.dy been hinted at by more than one observer. 

 The dark stripe is looked upon by most as the true contracting part of 

 the fibre, and they are termed the sarcous discs, or " Muskelprismen," 

 " Hauptsubstanz," or masses of " disdiaclasts," and the light stripes as 

 merely connecting matter, " zwischensubstanz," or " Muskelkastchen 

 flussigkeit." Dobie's line — more especially from the dipping down 

 and attachment of the sarcolemma in insects' muscle at this point — 

 has been looked upon (Krause, " Allgemeine und Mikroscopische 

 Anatomie," section Muskel System, pp. 80 — 90) as a delicate trans- 

 verse membrane. This view has received the assent of such micro- 

 scopists as Klein and Ranvier, but not of Wagener (" Jahresberichte 

 der Anatomie und Physiologie," Hofmann and Schwalbe) and 



