61 PHILOSOPHICAL TRANSACTIONS. [aNNO J/ 14. 



have greatly eased the labour of deducing the logarithms of the first prime 

 numbers, which appear to have cost him so much pains. 



Microscopical Observations on the Fibres of the Muscles, By Mr. Leuwenhoeck, 



F.R.S. N°339, p. 55. 



I send you a copy of my observations, concerning the membranes with 

 which the fibrillae of the muscles appear to be encompassed, both in the flesh 

 of a whale, cod-fish, salmon, and smelt; and also in that of beasts, from an 

 ox to a mouse; in all which the appearance was the same. 



The flesh of the whale, was a small piece cut off^ near the tail. Viewing 

 this through the microscope, I judged its fibres to be 4 times as large as 

 those I had formerly observed in another piece of whale's flesh, taken from 

 another part of the fish ; which made me consider, whether the fibres of that 

 part might not be the larger, for its greater strength. Cutting the said fleshy 

 parts lengthwise, and across the fibres, I discovered more plainly than before, 

 that each flesh-fibre was enwrapped in a fine thin membrane. 



To have a better idea of these flesh-fibres of a whale, I cut a thin slice of it 

 across, which I laid on a wetted piece of glass, that the flesh, which was very 

 dry and shrunk, might be swelled by the moisture, and thereby distended to 

 the natural size on the body of the fish itself. In this state, placed before the 

 microscope, it appeared as represented in fig. Q, pi. 3, in which the parts lay so 

 close together, that their encompassing membranes, represented by the black 

 lines, were but just discernible, some of them however appearing larger than 

 others : these, when attentively viewed, seemed plainly to be divided into mul- 

 titudes of others, cut also transverse, the size of which was no larger than a 

 common sand to the naked eye. These were so close crowded together, that 

 their figure was very irregular, and their sizes different; for though each seemed 

 encompassed with six others, yet some of them were twice as large as others. 



Having formerly mentioned the slenderness of these fibrillae in the flesh of a 

 whale, and judging these to be 4 times as large, I took a thin slice of the for- 

 merly mentioned whale-flesh, which I had still kept by me, and after having 

 made it thoroughly wet, I viewed it with the same microscope as I had done 

 this of the tail. This appeared as is represented fig. 10. When the moisture 

 dried away from these slices, so stuck on to the glass, the particles became 

 much smaller, and the membranes with which each was encompassed, became 

 very visible; viz. those that were not shrunk away; which was a very entertain- 

 ing object to the curious; and as often as I made new cuts, a new object pre- 

 sented itself. 



