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XII. Some additions to the Croonian Lecture , on the changes the 
blood undergoes in the act of coagulation. By Sir Everard 
Home, Bart. V. P . R. S. 
Read March 5, 1818. 
Several of my friends, much more deeply versed in mathe- 
matics than myself, who were present at the reading of the 
Croonian Lecture, remarked that no spherical bodies could 
be accurately measured by the common micrometer, and 
therefore no correct idea of the diameter of a globule of the 
blood could be obtained by that means. They were also led 
to doubt the appearance represented in the coagulum, being 
real, since air, in all ordinary circumstances, when let loose, 
forms itself into globules, not moving in straight or curved 
lines. 
These objections, coming from philosophers for whose 
opinions on such subjects I have the highest respect, induced 
me to request permission of the President to withdraw the 
Lecture, that I might correct any errors I had fallen into 
before the Paper came before the Committee. I found also 
upon reflection, that I had left the investigation more imper- 
fect than I was aware of, since it is of very little consequence 
whether, in the act of drying, coagulated blood puts on this 
particular appearance or not, if I cannot at the same time 
adduce proofs of the same changes taking place in coagula 
while they are still moist, and also in the blood when it is 
Bb 
MDCCCXVIII. 
