ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
407 
tremulous ami movements are not much impeded. If tlio Infusoria aro 
to be dissected the gelatin should be thinned down from 0*8 to 1 * 0 per 
cent. In order to transfer the animals to the gelatin, the Litter is warmed 
until it is just liquefied. A small quantity of it is poured into a watch- 
glass, a drop of water containing the animals is added to it, the two 
stirred quickly together, and a drop of the mixture placed on a slide 
(which may be ever so slightly warmed), and then the cover-glass at once 
put on. If it be desired to keep the Infusoria for some time in this 
gelatin it is well to make the preparation with the water which they in- 
habit, so that the Bacteria on which they live may be present for tlieir 
nutriment. 
Weaker solutions of gelatin are not at all harmful to the organisms : 
e.g. the author has found Paramecium aurelia and JEuglena viridis multiply 
wonderfully in a 0 • 5 per cent, solution. Stronger solutions set up a 
gradual granular degeneration, though in these the animals will remain 
unaltered for 3 hours, quite long enough for observations. Euglena 
viridis has, however, been kept for 24 hours quite motionless in strong 
jelly, and, after having been dissolved out with warm water, became 
quite lively again. 
Demonstrating Structure of the Embryo-sac.* — Mr. G. W. Martin 
has found the following process useful for demonstrating the egg- 
apparatus and antipodal cells in Sulidago and Aster. The material was 
fixed in 1 per cent, chromic acid for twenty-four hours, and stained 
with alum-carmine after washing ; again washed and dehydrated ; it 
was taken through the xylol-absolute-alcohol process into a saturated 
solution of xylol and paraffin ; it was then infiltrated with paraffin, 
imbedded, and cut with a microtome ; the sections were stained with 
Bismarck-brown and mounted in xylol-balsam. 
Giant Cells and Phagocytosis.^ — Dr. Knud Faber devised a 
method whereby he was able to demonstrate most convincingly that 
giant cells are intracellular digesting phagocytes ; the method consists 
in introducing into the subcutaneous tissue of rabbits gelatinized agar 
and then observing the resorption processes. The agar was dissolved 
in distilled water ; usually a 1^ per cent., but occasionally 3 per cent, 
solutions were injected, and immediately afterwards the injection site 
was cooled down with an ether spray so that the mass set in situ. It 
was then left for periods varying from 1 to 80 days. 
In no case were there any naked eye evidences of inflammation, the 
agar lying apparently unchanged, imbedded in the connective tissue. 
The pieces excised for microscopic investigation were fixed usually in 
Flemming’s fluid or in spirit, but sometimes in sublimate or picric acid. 
The stains used were safranin, alum-carmine, gentian-violet, and hsema- 
toxylin. The appearances observed were those of chronic inflammation, 
the pieces of agar being surrounded by leucocytes, epithelioid and giant 
cells. The agar pieces were not only surrounded by cells but were 
found within the cells. By colouring the agar with carmine or Berlin 
blue the digestive action of the giant cells was best seen. The opinion 
is strongly expressed that giant cells possess in a special degree the 
* Bot. Gazette, xvii. (1892) p. 353. 
t Journal of Pathology and Bacteriology, 1. (1893) pp. 319-58 (1 pi.). 
