HENDRY, ON TEICHMANN’S BLOOD-CRYSTALS. 17] 
graphical Dictionary’ fortunately supplies the deficiency, 
although I had myself accidentally stumbled upon its recom- 
mendations prior to my consulting it. Under the head of 
Heematoidine, which appears therein to embody the several 
kinds of blood-crystals, the author states, “ If recently dried 
blood be treated with a vegetable acid (acetic, oxalic), and a 
drop of the solution be placed upon a slide coverED witH 
THIN GLAss, and kept at a temperature of 80° to 100°, Fahr., 
the crystals may also be obtained, the addition of water and 
a little alcohol or ether to the blood sometimes favours the 
separation of the crystals—their preservation is difficult.” 
My own experiments have been conducted thus :—A drop 
or two of fluid blood, or if dry, with an addition of distilled 
water, may be placed upon a slide, and a small quantity of 
dried common salt be mixed with it, and spread through a 
disc of about the size of a shilling; lightly cover over to 
protect from dust, and set aside for a day or two for spon- 
taneous evaporation, then scrape off the hardened material 
with a knife edge, break up and spread loosely, moisten with 
glacial acetic acid, and apply a thin glass cover (square), 
filling up with the acid by means of a glass rod; place now 
upon the water-bath (a temporary apparatus, such as two tea- 
cake tins placed upon a tripod and heated with the spirit, 
may suffice), and when dry apply in like manner a few drops 
of distilled water with the glass rod, the cover not being 
disturbed ; continue the heat to dryness, examine under the 
microscope both slide and cover, reversing that which is 
most approved; then moisten with spirits of turpentine or 
chloroform, and mount in Canada balsam, in which will be 
found an admirable medium of preservation notwithstanding 
the difficulties asserted elsewhere. The -4,ths objective will 
constitute a power best adapted for observation, the crystals, 
although deviating much im size, yet for the most part 
are very characteristic. 
I have myself experimented several times very successfully 
upon a much less quantity than the usually estimated bulk of 
a drop of human blood. 
