12 THE AMERICAN MONTHLY (January, 
a perfectly fluid state, if protected from dust, dirt, and foreign bodies, which 
may serve as points from which coagulation may start and spread. It may be 
kept in this condition if drawn under oil, or into a vessel thoroughly greased. 
A vessel lined with vaseline affords an excellent receptacle for such experi- 
ments, and the blood will remain liquid in it for days if protected from dust, 
and if the surface is not allowed to dry. It may be stirred with a greased 
red, and still remain fluid. 
It seems to us this will afford an excellent means of investigation of the 
growth of certain organisms in blood. If the organisms to be cultivated can 
only be introduced without producing coagulation, much interest will be 
attached to any experiments upon their growth in the ftuid. He 
MICROSCOPICAL TECHNIQUE. 
CUTTING SECTIONS OF ANIMAL TISSUES.—Dr. James Reeves, of Wheeling, 
W. Va., contributes to St. L. Med. and Surg. Jour. (Dec., 1886), an article 
upon section cutting, which receives the name of ‘ Reeves’ method.’ We will 
recapitulate its chief points, none of which are, however, new in histotomy :— 
1. The tissue is to be first well soaked in ice-cold water, when as fresh as 
possible, for one hour or two; then in small pieces about $ in. square and 4 
in. thick, placed in twenty times its volume of absolute alcohol. The alcohol 
should be changed as often as it becomes cloudy, and the hardening should 
occupy several days, though it may be performed, if haste is necessary, in 
twenty-four hours. 
2. Clearing and embedding.—After complete hardening and dehydrating 
in absolute alcohol, the specimen is to be transferred to spirits of turpentine 
or benzole, to remain from thirty minutes to twelve hours, until thoroughly 
permeated or cleared. Then transferred to bath of melted paraffin, at tempera- 
ture of not more than 140° F. (= 60° C.), to remain from fifteen minutes to 
S or 10 hours, according to the density. The time in the bath may be deter- 
mined by the disengagement of air from the specimen, and is concluded when 
no more bubbles are given off. 
3. After this interstitial imbedding, the ‘ cast’ is ready to be made. For 
this, take a piece of writing paper and spread it on any plane surface, and 
pour on it paraffin till it forms a mass of the diameter of a quarter of a dol- 
lar. Then, before the paraffin has had time to harden firmly, lift the prepa- 
ration from the bath, place it on the cooling parafhin, press it gently down 
with the finger, set a mould around it, and pour melted paraffin over it until 
the mould is full. If the process has been properly performed, the tissue 
will be entirely surrounded and permeated with paraffin. If, in any part, it 
is not hard and firm, and well attached to the paraffin, the operation is a 
failure. 
4. The mass then embedded is to be cut in the microtome, or otherwise, 
and the sections then placed upon the slide. The slide first receives a coat- 
ing of a mixture of collodion, t pt.. and oil of cloves 20 parts, and the section 
is laid upon this. The slide with the section is now heated at not over 130° 
F. till the paraffin is melted, plunged in turpentine, and left until it is cleared. 
5. Staining is now applied. The slide, with the cemented section, is 
transferred from turpentine to 95” alcohol, and kept there until the turpentine 
is washed out. The stain is now applied. 
6. For a mounting medium, balsam ‘ cut with’ collodion is recommended, 
and the cover-glass finishes the operation. 
jullie: 
MEASURING REFRACTIVE INDEX.—Some time ago Professor H. L. Smith 
described a convenient and very simple device for this purpose, which afforded 
