688 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
form will always sink as soon as paraffin is added. 2. Place the tissue 
in a warm chamber heated to 30° C. for twenty-four hours. 3. Place 
the tissue in a warm chamber heated to the melting-point of the paraffin 
(46° C.), and after six hours replace the ordinary cork stopper (which 
up to this stage has always to be employed) by a perforated one. This 
method is adopted to ensure a gradual giving off of the chloroform, for 
I find that, if the latter be driven off rapidly, a good deal of shrinkage 
always results. When all the chloroform has evaporated, i. e. if after 
shaking the bottle gently one is unable to detect by smelling the faintest 
trace of chloroform, then the tissue is ready for sectioning. If the 
bottle be not shaken gently before smelling the solution, it is often im- 
possible to detect chloroform, although a large quantity of the latter is 
still in the lower layers of the paraffin, as the upper layers part more 
readily with the chloroform. 4. The tissues should not be exposed 
longer than just necessary to the temperature of melted paraffin, but 
should be imbedded by means of Leuckart’s type-metal box, or by two 
L-shaped pieces of metal running in an oblong box, the breadth of 
which corresponds to the short limb of the L. The metal boxes should 
be warmed and filled with melted paraffin. After five to twenty seconds, 
w r hen the paraffin at the bottom of the box has solidified, the tissue is 
removed from the bottle by a copper lifter, and, without being allowed 
to cool, it is dropped into the imbedding box, put into any desired 
position by means of hot needles, and the paraffin cooled very gradually. 
It is best not to touch the tissue with any instrument till it is ready to be 
placed in the imbedding box, and also to avoid heating the copper 
lifter or the needles too much. Tissues thus imbedded may be kept 
unchanged for any length of time. 
To get perfectly satisfactory results, the tissue we are treating must 
be living ; smaller vegetable objects, as flower-buds, ovaries, growing 
apices, &c., must be dropped into the fluid as soon as separated from the 
plant, and animals like tadpoles, worms, and larvas are placed directly 
into the fluid, where they are killed rapidly and in an extended position. 
Tissues of plants and animals must be placed in the fluid as soon as 
separated by dissection. Tissues of warm-blooded animals should be 
placed in the picro-corrosive alcohol of corresponding warmth. Treat- 
ing tissues like brain, it is best to place into the bottom of the vessel a 
pad of cotton-wool or felt to allow the hardening fluid to penetrate 
readily ; the pad must be removed before the chloroform-alcohol is 
placed below the tissue. My method was found to give very satisfactory 
results with plasmodia of myxomycetes, growing apices, developing en- 
dosperm, stem and leaf structures, human foetal brain, frog’s cartilage, 
muscle, myxomatous tissue, retina, tadpoles, wasp larvae, caterpillars, &c. 
Karyokinetic figures are specially well fixed, and show the minutest 
details. 
Now a few words as to mounting sections. Sections cut in ribbons 
(I use the Cambridge rocking microtome) are fixed to a slide by Schalli- 
baum’s method, thus : — An even layer of the fixing material is spread on 
the slide, the slide heated to 30° C. (melting-point of paraffin = 46° C.), 
and a piece of the ribbon gripped by a pair of forceps at one end and 
quickly laid down on the warm slide. In this way I get the sections to 
lie perfectly flat, and it is even possible to make a closely coiled-up 
