THE DIAGNOSIS OF BLOOD STAINS. 23 
of adjusting an objective to the same degree of accuracy as the 
optician. He believed that with the particular class of objects 
mentioned by Dr. Dippel no two histological observers would be 
found to agree as to what was the best correction. He further 
stated that Prof. Abbe had met that difficulty by proposing a special 
test object for the purpose, a description of which was being pre- 
pared for the Journal. The test plate showed beyond question 
what the best correction was, so that it was possible for a micros- 
copist to pass a number of objects under the objective and at once 
determine the best correction for each. Mr. Beck stated that Dr. 
Dippel, in his remarks for abolishing the correction collar, seemed 
to be content with inferior definition rather than take the trouble 
to get the best that was to be obtained. Mr. John Mayall, Junr., 
concurred in much that Mr. Beck had said, and advised the cor- 
rection collar to be applied to homogeneous immersion lenses, and 
the Society would be glad to know that Prof. Abbe himself had so 
far wavered from his former opinion that he now agreed with Dr. 
Zeiss, and in future all homogeneous immersions supplied by him 
would be made with or without correction collar. 
We would like to add that ever since their introduction, Dr. 
J. Edward Smith, who is a splendid manipulator of objectives, has 
always argued for the addition of the correction collar to homogene- 
ous immersion objectives. —Ep. 
THE, DIAGNOSIS; OF BLOOD STAENS: 
R. J. G. RICHARDSON, of Philadelphia, has given the 
following summary of his measurements of blood corpuscles. 
It was originally printed in Gaillard’s Medical Journal, and repro- 
duced in the American Monthly Microscopical Journal, from 
whence we take it :— 
first—That in unaltered blood-stains, as ordinarily produced 
by the sprinkling of drops of blood upon clothing, leather, wood, 
metal, etc., we can, by tinting with anilin or iodine, distinguish 
human blood-corpuscles from those of the ox, pig, horse, sheep and 
goat, whenever the question is narrowed down by the circumstances 
of the case to these limits. 
Second—By the method I have devised we can measure the size 
of the corpuscles, and apply the two corroborative tests of tincture 
of guaiacum with ozonized ether and of spectrum analysis, to a 
single particle of blood-clot weighing less than one fifteen-thousandth 
part of a grain, a quantity barely visible to the naked eye. 
Third—Hence, when an ignorant criminal attempts to explain 
