and Circulation of the Blood .' 127 
carried along the Veffels, changes in a mofl 
furprizing Manner. 
In Spring-time, if a little Frogs Spawn be 
kept fome Days in a fmall Quantity of the 
Ditch-Water wherein you found it, you will 
be furnifhed with a Number of exceedingly 
fmall Fadpoles , which, when firfl they be¬ 
gin to fwim, are almoft wholly tranfparent y 
and if placed before the Microfcope, in a 
Tube proportionably fmall, with fome Water 
in it, you will eafily difcern the Heart and its 
Pulfation, together with the Blood circulat¬ 
ing in every Part of the Body ; and, particu¬ 
larly, in the Tail more than fifty Veffels 
prefent themfelves at one View. 
Thefe Fadpoles become lefs clear every 
Hour, and in a Day or two their Skin grows 
fo opake that the Circulation of the Blood 
can be feen no longer, unlefs it be in the 
Tail, or better Fill in the Fins, at the join- 
ing-on of the Head. 
A fmall Mufcle taken carefully from its 
Shell, and placed before the Microfcope on 
an Iiinglafs, affords a View of many; Arteries 
and Veins, through which the Circulation 
of the Blood may be very clearly feen : and 
one great Advantage in this Object is, that 
it lies always quiet whereas moil* other 
Creatures are difficult to be kept flill long 
enough for Obfervation. The Motion of the 
K 3 Blood 
