Sir Everard Home on the changes , &c. 173 
degrees, and comparing, with the nicest discrimination, what 
was exhibited by one magnifying power, with what was 
shown by that immediately above it, and, where they did not 
exactly correspond, employing the whole energies of his 
mind, with a patient labour, almost beyond what is natural, 
in ascertaining the cause of the deception which must in one 
of them have taken place. To the observations of such a man 
upon subjects of this nature, if we are not confidently to place 
a reliance, how are we to give credit to the remarks that are 
made by common observers ? 
1 have said thus much as an introduction to the observations 
that I am going to bring forward, for the public to know, 
whatever opinion they may form of them, they have been the 
result of long and unwearied research ; and have been so fre- 
quently repeated as to satisfy Mr. Bauer of their correctness. 
The red globules of the blood in the human body, when 
enveloped in their colouring matter, appear, when measured 
in the microscope by the micrometer, to be 7 / 5 5 - part of an inch 
in diameter, requiring 2,890,000 to a superficial or square inch. 
These globules, when deprived of their colouring matter, appear 
to be 20^00 P art an inch i n diameter, which makes 4,000,000 
of globules to a square inch. From these observations, it ap- 
pears that the globules, when deprived of the colouring mat- 
ter, are not quite one fifth part smaller. The colouring 
substance appears not to be contained in the globules, but 
only to envelope them : one reason for forming this opinion 
is, that the separation is very rapidly effected, the colouring 
substance flowing from all parts of the globule at the same 
instant, and that to retain the globules in the coloured state 
it is necessary that a very small quantity of blood only be 
