582 PHILOSOTHICAL TRANSACTIONS. [aNNO 1 682-3. 



that fall down; whether through want of sun, rankness of grass, weeds, or 

 other accidents. So in the womb, each animalcule might suffice for a genera- 

 tion, if the place where it comes to be nursed be fit for it; but the womb being 

 so large in comparison of so small a creature, and there being so few vessels and 

 places fit to feed it, and bring it up to a foetus; there cannot be too great a 

 number of adventurers, when there is so great a likelihood to miscarry. 



It may be asked again, why a woman brings forth only 1 or 2 children, since 

 if there were but two proper places in a uterus, several of the animalcules might 

 there be fed. I answer, it may happen to these animalcules, as it does to 7 or 

 8 seeds put into a small hole of the ground ; that seed which puts out the largest 

 and strongest root, starves all the rest, and becomes a tree. It may be asked 

 me again, why I make the animalcules found in the seed of several animals to 

 be of such different sizes, comparatively to the animals they belong to, viz. in 

 the space of a small sand in the seed of a cock, 50,000; in the row of a cod- 

 fish 10,000; in the row of a ruft^ which fish is 1000 times less than a cod-fish, 

 the animalcules as large as the others. Whereas it seems reasonable that the 

 animalcules ought to be in size to one another, as the creatures in which they 

 are found; from whence it would follow, that those animalcules which are in 

 insects, would never be capable of being discovered, because of their exceeding 

 smallness. I answer that we must satisfy ourselves in these things as well as we 

 can; for, not to speak of a cocoa-nut, a great wall-nut with its green shell 

 weighs down 1000 apple tree seeds, and yet the proportion between the trees is 

 not so great. 



In my letter of the third of March l681-2 I described the texture of a flesh 

 and fish-muscle; but have since examined that of a flea, judging that if I could 

 find the same filament, I might be positive that the muscles of animals are all 

 of the same make; having therefore several times separated and exposed to view 

 that muscle of the breast, to which the leg is partly fastened ; I observed 

 the same ring-like inden tings in the filaments, that I had seen in other places. 

 Some appeared to me thicker in the middle then at the ends, as fig. 13, pi. 13, 

 ABCDEFGH is the description of the filament of a flea broken out of the 

 breast, from which I perceived the filaments of this insect to grow tapering to- 

 wards the ends, and lose themselves in a membrane or tendon, like the fila- 

 ments of the muscle of an ox. Some of the indentings were as CF, but most 

 throughput were as ABGH. Several times I had an appearance as if a fila- 

 ment were constituted of several lesser threads joined together, and lying by the 

 sides of each other. In pursuing my observations, I took some of the flesh of 

 the legs of the flea, and found it like that of the breast; here I counted 12 of 



