90 PHILOSOPHICAL TRANSACTIONS. [aNNO I7OS. 



far superior to any of Mellins ; particularly the greatest magnifiers augment 

 more, and yet show an object more distinct than his do. The greatest shows a 

 hair of the head considerably above an inch diameter, and some eyes see it at 

 least two inches; but supposing it a bare inch, and that, as Mr. Hooke affirms, 

 640 hairs breadth makes one inch, the length and breadth of an object will by 

 it be enlarged 640 times, the surface 409600, and the solidity 262J44000. 

 But the best of our glasses must needs fall bhort in power and goodness of M. 

 Leuwenhoeck's ; and though some persons question the truth of his relations, 

 yet as far as I am able to follow him (and I have tried mnny of his experiments) 

 I find him always faithful in matter of fact, and therefore question not his 

 veracity in other things. 



One of the first objects I tried my glasses by, was a living louse, in which I 

 could plainly see the motion of the muscles, when he moved his legs, which 

 are all joined in a longish dark spot in the middle of his breast, where the 

 tendons seem all united. The like motion of muscles is also visible in the head 

 when he moves his horns, and in the several articulations of his legs. I saw 

 also clearly a multitude of various branchings of arteries and veins, and the 

 pulse regularly beating in several arteries. But the most entertaining sight is 

 the peristaltic motion of the intestines, which is continued from the stomach 

 through all the guts to the anus. I have observed the like peristaltic motion in 

 a flea, and in several sorts of small transparent maggots and caterpillars. But 

 a louse is the most convenient, as it will bear rougher handling, and live con- 

 fined between two concave plates, if not crushed, for 4 or 5 days. 



I thought a mite would also prove a good subject for the microscope; but found 

 them not so transparent as I expected. However I plainly saw, that all the 

 bristles on the body of one of them (which to a common single glass, and to 

 the greatest magnifier of my three glassed microscope look like plain smootii 

 hairs) were, when viewed with a large magnifier, all spicated, or bearded like 

 the ear on the seed head of some grasses, the appearance was like fig. a, pi. 1, 

 and every bristle on the whole body and legs, both long and short, had the 

 same formation. But all mites are not so ; for of 7 or 8 inclosed together, I 

 found only one whose bristles were of this make, in the rest the horns only 

 were spicated. Whether they were of different kinds, or rather only of diflTer- 

 ent sexes, I cannot determine ; but they were all taken out o{ the same cheese 

 at the same time, and were in other parts very like Their mouths open hori- 

 zontally, to the right and left, like that of a wasp, and hard headed maggot. 

 After being some days shut up together, some were found dead, and the survU 

 Tors preying on them, which gave me an opportunity of observing their manner 

 of feeding, which was very remarkable, for they thrust one mandible forward. 



