THE LEG-MUSCLES OF THE WATER-BEETLE. 
439 
ances observed ; some histologists, however, e. g. Kolliker, were disposed to regard fibrils 
extending from one end of the fibre to the other as the ultimate elements of the muscle. 
In the year mentioned, Krause, in a paper on the subject*, drew particular attention to 
the transverse line in the centre of the bright band, and, looking upon this as the optical 
section of a fine membrane stretched transversely across the fibre, described the latter as 
being divided into a number of flat compartments ( Muskelfdcher ), each containing a disk 
of solid substance in the centre, separated from the membrane above and below by fluid. 
At the same time, taking the fine lines bounding the polygonal areas described by 
Cohnheim in transverse sections to be the optical section of similar membranes 
running parallel with the axis of the fibre, and of course meeting the others perpendi- 
cularly, he described the flat compartments as thus subdivided into a number of muscle- 
boxes ( MuskelJcastchen ), each of them bounded by membranes both at the ends (bases) 
and sides, each base-membrane being common to two contiguous muscle-boxes. Each 
muscle-box, he considered, is almost filled by a portion of the dim substance (muscle- 
prism), this being separated from the base-membranes by fluid. Subsequently Krause 
described the muscle-prisms as consisting each of a bundle of more minute particles, which 
he termed muscle-rods ( Muskelstabchen ). [The transverse line bisecting the clear stripe 
was known long previously to Krause’s paper on the subject. It was described by Busk 
and Huxley f as occurring in the muscles of insects ; and since they observed with 
marvellous correctness that it was not so much a continuous line as a succession of 
contiguous dots, it was supposed by them to be due to the existence of a row of minute 
sarcous elements interpolated between the rows of larger ones, which were regarded 
as forming the darker stripes of the fibre. The rod-like character of the so-called 
sarcous elements had also been long known : it was distinctly figured by Brucke ; and 
Sharpey had more lately drawn attention to the close connexion which exists between 
these rod-shaped particles and the minute dots composing the transverse line, only just 
falling short of tracing the one into the other — this, too, both in the muscles of insects 
and in human muscle^.] IIensen §, writing about the same time as Krause, gave a 
somewhat similar account of the structure of muscle, also drawing especial attention to 
the apparent membrane bisecting the light stripe ; as regards some points, however, his 
account was eniirely at variance with that given by Krause. 
The next contribution to the subject of any importance was that of Heppner||, who 
employed the still living contractile fibres of Hydrophilus piceus. He assumed the dark 
transverse line in the middle of the clear stripe to represent a continuous disk composed 
of a substance (‘ Zwischensubstanz ) possessing a lower index of refraction than the rest of 
the fibre, and endeavoured to show, by the assistance of a diagram, that the bright 
* “ Ueber den Bau der quergestreiften Muskelfaser,” Zeitschr. f. rat. Med. xxiii. 
t Kulliker’s ‘ Manual of Human Histology.’ Sydenham Society’s Translation, 1853. 
t Quain’s ‘ Anatomy,’ 7th ed. 1867, vol. i. p. cxix. 
§ Arbeiten aus dem Kieler physiologischen Institut, 1868. 
|J “Ueber ein eigenthiimliches optiscbesVerbalten der quergestreiften Muskelfaser,” Scuultze’s Archiv, v. 1808, 
3 n 2 
