Of the Semen Mafculinum. 105 
ceive the formation of all the vertebrae, with the blood- - 
veffels and ramifications palling over them, and could 
fee the fpinal marrow in two places *, and diftinguifhed 
not only the head, but alfo the mouth, brain, and eyes, 
the bignefs of two grains of fand, and clear as cryflal ; 
he likewife faw the ribs and inteflines, though the whole 
creature was no longer than the eighth part of a pea. 
After which he opened the uterus of another ewe k , three 
days from the coitus, and fearching the liquor coming 
therefrom with a magnifying glafs, obferved a little par¬ 
ticle the fize of a grain of fand ; and examined it with a 
very good microfcope, and with great pleafure found it 
to be an exceeding minute lamb, lying round in its in¬ 
teguments, and could plainly difcern its mouth and eyes. 
The human femen has alfo been viewed by the mi¬ 
crofcope, and found to be as plentifully flocked with 
animalcules, as that of other animals: Mr. Leeuwen¬ 
hoek has feen more than ten thoufand living creatures 
moving in a quantity of the fluid part thereof, no bigger 
than a grain of fand : and in the thicker parts, they 
were fo thronged together, that they could not move for 
one another; their fize was fmaller than the red globules 
of the blood, and even lefs than a millionth part of a 
grain of 1 fand, their bodies roundifh and fiat before, as 
in fig. 172. but ending fharp behind. Their tails are 
exceedingly tranfparent, and five times longer, and fien- 
derer than their bodies. They move by the agitations 
of their tails in various windings, after the manner that 
eels fwim. 
The m animalcules in the femen mafculinum of all 
creatures differ but little in fhape or bignefs, for which 
reafon 
5 Arc. Nat. Tom.i. Part ii. p. 164. k Ibid. p. 173. 
* Arc. Nat. Tom. ii. Part ii. p. 61, q6, 286. m Ibid, 
i om. lv. p. 3O0 
