VOL. XXXI.] PHILOSOPHICAL TRANSACTIONS. 525 



is no thicker than the edge of a knife, is marked by epg. When these muscles 

 had lain several days on a paper, they were not yet dried so hard, but that 1 

 could split them into thin shivers, one of which is shown between the letters 

 I and K in fig. 12, in order to show the oblique course of the fibres, which 

 are represented by small lines. 



I now turned my thoughts to the River-Fish, and particularly to the pearch ; 

 and, as I imagined that an old pearch had no greater number of muscular 

 fibres than a young one, but only that the fibres increased in size during the 

 growth of the fish, and that the larger these fibres were, the more plain and 

 distinct mast be the small vessels of which they were composed ; I procured 

 one, the largest I had ever seen, weighing 3-i^lb. and 17-f inches in length. 

 Delft measure, which is the same with the Rhinland.* 



I cut oflf" four pieces from this fish in diflferent parts, and viewing the mus- 

 cular fibres both in length and breadth, I found that the fibres of this great 

 pearch were not so thick as those of the cod-fish. On cutting them through 

 lengthwise, I saw the apertures of the small vessels in vast numbers. I next 

 cut some of the fibres transversely, and found them thinner in this pearch, 

 than in a middling cod-fish, and saw the small vessels, that compose the greatest 

 part of the bulk of the fibre, lying as close together, as ever I saw them in 

 any kind of fish or flesh. 



Fig. 13 represents a small portion of these muscular fibres of the fish, cut 

 through transversely, after they were grown dry, and in their shrinking had 

 been torn off from the small vessels that encompass them. The openings of 

 the small vessels in these fibres were distinctly to be seen, but appeared in such 

 great numbers, and were so exceedingly small, that it was impossible to repre- 

 sent them any otherwise than by points. In this figure are represented what 

 we call the membranes, but which indeed are nothing else but a congeries 

 of small vessels, which not only surround the fibres, but enter into their very 

 substance. These, in the drying and shrinking of the object on the plate, 

 had been torn off from the fibres, as may be seen at p, p, p. 



I next put a small drop of water, about the size of a pin's head, on this small 

 portion of fibres, into which it immediately insinuated, and swelled them to 

 the same size as when they were first laid upon the plate: after which, they 

 were drawn as they then appeared, but omitting the small vessels, and only 

 showing the circumference of every fibre, as appears at fig. 14. I then split a 

 grain of millet through the middle, and placing one half of it on the glass, 

 near the portion of fibres represented in fig. 13, I observed that the half grain 



* Nearly the same as the English. 



