ioS Some Account of the Blood . 
In order to obtain this ufeful Knowledge, 
it will be neceffary to examine the human 
Blood and other Juices, frequently, with the 
Microfcope, in every Condition, and under 
every Diflemper, as well as in a State of 
Health : by which we fhall have ocular De- 
monftration of its different Appearances in 
each State, and of the Changes it undergoes; 
and by Experiments of various Mixtures with 
it, may poflibly difcover by what Means it 
can be altered from one Condition to another: 
as from a thin and broken to a more firm 
and confident State, and fo on the contrary. 
Would our learned Phyficians, who are 
heft able to judge of fuch Matters, be indu¬ 
ced to take this Method into their Practice, it 
is reafonable to believe, that in a few Years 
the Caufes of Difeafes would be better known, 
and the Art of Healing brought to a much 
greater Certainty, than it is at prefent. An 
Obfervation of Mr. Leeuwenhoek is veiy 
well worth regarding : he took Notice, that 
when he was greatly difordered, the Globules 
of his Blood appeared hard and rigid, but 
grew fofter and more pliable as his Health 
returned : whence lie infers, that in an 
healthy Body it is requifite they fhould be 
foft and flexible, that they may be capable 
of palling through the capillary Veins and 
Arteries, by eafily changing their round Fi¬ 
gures into Ovals, and alfo of re-affuming 
their former Roundnefs when they come 
into Veifels where they find larger Room, 
