1887.] MICROSCOPICAL JOURNAL. 163 
After the specimens have hardened sufficiently they may be washed in 
water or placed at once in dilute alcohol ; stronger alcohol is added gradu- 
ally until ordinary commercial is used, in which the tissues may be preserved 
indefinitely. 
The tissues may, now be cut by the old or wet method; but usually a pro- 
cess of interstitial imbedding is used and the prepared tissue is cut dry. 
INTERSTITIAL IMBEDDING. 
The advantages of interstitial imbedding are that by it individual elements 
are supported during the cutting and the relations of the elements preserved, 
and at the same time it renders possible the cutting of sections of extreme 
thinness. 
Paraffine has been used for some time as an interstitial imbedding mass. 
A method of section cutting by the use of paraffine as an imbedding mass 
was described by Dr. Reeves, of Wheeling, W. Va., in an article in the S¢. 
Louis Med. & Surg. Journal, Dec., 1886, which was recapitulated in the 
American Monthly Microscopical Journal, Jan., 1857, with a just editorial 
criticism. 
Dr. Reeves’ method is essentially the same as had been used in the Army 
Med. Museum and in my own laboratory for some time. 
Paraffine for this purpose should be bluish, transparent, and ring slightly 
when struck, and its melting point should be suitable to the temperature of 
the laboratory. I find 135°. F. to be a suitable melting point for general use. 
By melting together the fede and softer kinds any “desired melting point 
may be obtained. 
Some solvent of paraffine is used to prepare the tissues for the bath of 
melted paraffine ; those most used being turpentine and chloroform. 
The specimens are first dehydrated in absolute alcohol, then placed in a 
bath of the soivent, and then in a solution of paraffine dissolved in the solvent, 
_ and finally in a bath of melted paraffine, and allowed to remain until thor- 
oughly infiltrated. The process is the same, no matter what solvent is used, 
but turpentine is now more used than chloroform. 
The time required for these different baths varies with different tissues, 
and cannot be definitely given. 
The important point of difference between this method and that advised 
by Dr. Reeves is the use of an intermediate bath of paraffine dissolved in the 
solvent used, thereby preventing the great shrinkage which will occur if the 
specimens be transferred dzrect/y from the chloroform or turpentine into the 
pure paraffine. 
The specimens are imbedded in fresh paraffine in paper trays, and after 
cooling may be cut, or kept in the blocks until wanted, in the dry state. 
The sections are cut on a sliding microtome, with the knife nearly at a 
right angle. They are cut into turpentine, or, preferably, benzole, in which 
the paraffine is dissolved out, and are then washed in alcohol and stained. 
Tissues may be stained zz 6w/& before infiltrating, and may then be mounted 
from the benzole, in balsam. Much time is saved by this method. 
Many of the common stains will do, but an alcoholic solution of borax 
carmine is the most useful. A little alcohol added to any of the common 
borax carmine solutions will answer every puppet After staining 12 to 24 
hours the pieces are placed in 70% alcohol, 100 c.c. and hydrochloric acid, 2 
c.c.; in this mixture the color changes from a dark maroon to a bright red ; 
they are then washed in common alcohol, dehydrated, and infiltrated as te 
fore described. 
For success in the paraffine method it is essential that the following points 
be remembered :— 
