Royal Society. 171 
conveyed all over the body 5 the three tricufpii Valves in the 
right, and the two mitral Valves in the left ventricle of the 
heart, oppofing its return into the veins, and the lemilunar valves 
of the Arteria pulmonalis and Aorta, preventing its ingrefs into 
the ventricles, are lufficient to demonftrate the ncceiTity of a cir- 
culation of the blood. 
Micro fcopcal ObfervationSj by Mr. J. Harris. Phil. Tranf. 
N° 220. p. 254. 
MR. Harris examined a fmall drop of rain-water, that had 
flood in a galley-pot in a window for about two months ; 
he took it with the head of a Imall pin from the dilcoloured fur- 
face of the water, and in it heobferved 4 forts of animals j in the 
clear part of the drop were two kinds, and both very fniall ; 
fome were of the figure of ants-eggs, thefe were in a continual iwift 
motion 5 and he found that this kind of oval figure is the moll 
common to the AnimakulA found in liquors 5 the other fpecies, 
that were in the clear part of the drop, were mors oblong, 
about three times as long as broad ^ thelc were exceeding nume- 
rous, but their motion w'^as flow in comparifon of the former. In 
the thick part of the drop, for the water had contraded a thickidi 
fcum, he alfo found two fpecies of animals, as a kind of eels, 
like thofe in vinegar, but much fmaller, and with their extre- 
mities fharperj thefe would wriggle out in the dear part, and 
then fuddenly betake themfelves back again, and hide themtelves 
in the thick and muddy part of the drop, much like common 
eels in the watery he faw here alfo an animal like a large mag- 
got, which would contract itfelf into a fpherical figure, and 
then extend itfelf again 5 the end of its tail appeared with a fore- 
ceps, like that of an ear-wig 5 and he could plainly fee it open 
and fhut its mouth, from whence air-bubbles would frequently be 
difchargcdj of thefe he could number about 4 or 5, and they 
feemed'to be buly with their mouths, as if feeding. Thele four 
kinds of living creatures he afterwards found in many other drops 
of the fame corrupted water, in the film and fcum, which was 
on the furface 5 for under that, in the lower parts of the water, 
he could never find any animals at all, unlefs when the water was 
difturbed, and the furface ihook down into, and mingled with 
the lower parts. 
With a much better microfcope he examined fome ram-water, 
that flood uncovered a pretty while, but had not contra6led any 
fuch thick and dilcoloured fcum, as that abovementioned had 5 in 
this, when it was clear, he could not find any animals at all ^ but 
Y ^ a little 
