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LV. A Main Cause of Discordant Views on the Structure of 

 the Muscular Fibril. By Martin Barry, M.D., F.R.S., 

 F.R.S.E.* 



[With a Plate.] 



I LATELY had the pleasure, on more than one occasion, of 

 examining muscle at Glasgow with Prof. Allen Thomson. 

 The microscope used was one of first-rate excellence by Smith 

 and Beck. We saw the states in Plate V. fig. 2 ab and ikl — 

 drawings sent me a few days after by the Professor, accompanied 

 by the following description and remarks : — " Portions of three 

 different muscular fibrillar from the Frog, presenting various 

 aspects, ab, a fibril splitting into two at c, viz. cd and ce ; the 

 part ac is probably double ; ce and cd are single, db appears 

 single ; but it is possible that it may be double, as e seems to 

 have been separated from c to d. From a to c the quadrilateral 

 form of the sarcal particles and the clearer intervening substance 

 prevails ; in ce and cf the oval and oblong quadrilateral ; from 

 ftod the rhomboidal ; and from d to b the rhomboidal, with an 

 appearance of spiral or twist in the intervals. — g and h are por- 

 tions of another fibrilla, in which the quadrilateral form of the 

 particles, and the distinction between them and the intervals, 

 are particularly well marked ; in g the upper surface is in focus, 

 and the cross mark in the intervals is not seen ; in h the focus 

 is adjusted for the deeper or further side, the intervening sub- 

 stance is crossed by a distinct transverse line, and each dark 

 quadrilateral particle presents a central spot, or rather a slightly 

 crucial mark in its centre. Although the portion of fibril here 

 represented appears quite single, I think I can see that at the 

 end a portion of it, not represented in this figure, is split into 

 two smaller fibrils. — ikl, two fibrillar separated at one part and 

 united in another ; a dislocation of the particles having taken 

 place, so as to produce an appearance of spiral form even more 

 distinctly than the drawing represents. / seems single ; but it 

 may be doubted, from what has been observed in following out 

 other fibrillar of the same form, whether the part ending at k is 

 reduced to its smallest elements. The specimen above described 

 has been preserved for three or four years in the moist state in 

 weak spirit or glycerine, I am not sure which. I think it is one 

 which, along with others, I received from Dr. Dobie f. — A. T." 

 The Professor adds : — " In the upper figure, ab, you will see 

 that I have suggested in the description the possibility of the 

 part from b to d being double. I am induced to think so, both 



* Communicated by the Author. 



t Dr. William Murray Dobie, at present one of the house surgeons in 

 the Royal Infirmary of Edinburgh.-— M. B. 



