170 HENDRY, ON TEICHMANN’S BLOOD-CRYSTALS. 
effusions, coagula or extravasations, thrombi, &c., and pre- 
senting the usual play of colours by chemical treatment 
similar to the colouring matter of bile; being also insoluble 
in water, alcohol, ether, or acetic acid. (See Virchow, p. 145 ; 
Kolliker, p. 526.) 
Hemin crystals of Teichmann, on the other hand, are not 
of pathological import, do not occur spontaneously, but are 
prodnced artificially and out of the body. 
Another form of crystal is designated hemato-crystalline 
of Lehmann. These differ in different classes of animals, 
are very destructible, and readily perish, are found in normal 
perfectly fresh blood outside the body only, are soluble in 
acetic and nitric acids, and also in caustic alkalies; they are 
red or colourless crystals, assuming the form of needles, 
columns or plates, probably belonging to the rhombic system, 
but also occur as tetrahedra, octohedra (guinea pig, rat, 
mouse), or as hexagonal plates (squirrel), &c. 
It may now be desirable to enter upon the subject of 
manipulation—recording the several brief methods for the 
production of Teichmann’s crystals, as set forth by authors, 
and furnishing also such details as I have found myself the 
most advantageous in the course of my own investigations. 
A blood-stain is treated with distilled water, and the 
solution, to which is added a little common salt, is evaporated 
in vacuo over sulphuric acid, then wetted with glacial acetic 
acid and evaporated on the water-bath, afew drops of distilled 
water being added to the product. Teichmann’s crystals 
may thus be examined (‘ Kolliker,’ 1860, p. 526). 
Again, the best mode of proceeding is to mix dried blood 
in as compact form as possible with dry crystallized powdered 
common salt, and then to add to this mixture glacial acetic 
acid, and evaporate at a boiling heat; this is a reaction which 
must be ranked among the most certain and reliable ones 
with which we are acquainted (‘ Virchow,’ 1860, p. 146). 
M. Briicke directs to “‘ wash the spots with cold distilled 
water to the reddish solution obtained, add a solution of sea- 
salt, and evaporate to dryness in vacuo over a vessel con- 
taining sulphuric acid; examine the dry residue well by the 
microscope, to verify whether it contains airy matter which 
might be mistaken for Teichmann’s crystals ; then add a little 
glacial acetic acid, evaporate to dryness, moisten the residue 
with water, when crystals of heematine will be formed if blood 
exists in the spots.” 
One might reasonably suppose, after the above several 
quotations, that nothing could remain to be added, and yet 
in experiment sources of failure may still exist. The ‘ Micro- 
