1 86 Sir Everard Home's additions to 
extravasated, and coagulates in the interior parts of living 
animals. 
I have therefore reconsidered this subject, and with the 
assistance of Mr. Bauer, have instituted a series of experi- 
ments, and had drawings taken to elucidate their results, 
which I hope will do away the objections made against coa- 
gulated blood having channels formed through it by the 
extrication of carbonic acid gas ; and prove, not only that the 
same change takes place when blood is extravasated in 
living animal bodies, but that these channels have a com- 
munication opened between them and the neighbouring 
arteries, and that the fluid blood circulates through the 
channels in the coagulum. In laying these experiments and 
drawings before the Society, I request that I may be indulged 
in adding them to the Croonian Lecture ; and with these addi- 
tions, that it may be submitted to the judgment of the CounciL 
As the measurement of spherical bodies is a subject on 
which I am totally unfit to form an opinion, I requested my 
friend Captain Kater to have the goodness to measure the 
diameter of a globule of the blood, in what appeared to him 
the most satisfactory manner, and to explain to me the mode 
of doing it. He very readily complied with my request, and 
the following is the mode which he adopted. 
A ruler divided into inches and tenths was placed on the 
box which supports the microscope, a mother of pearl mi- 
crometer scale was placed under the microscope, each division 
of which was equal to one two-hundredth of an inch: viewing 
this with both eyes open, its image appeared to be projected 
on the ruler, and one division appeared to subtend the space 
of one inch. The micrometer scale being removed, blood 
