682 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the two, &c. — and stopped with cotton. The coating is done by pouring 
into the tube a quantity of medium, tipping and turning the same until 
no part of the surface remains untouched, except, of course, that in the 
immediate vicinity of the cotton stopper. When the medium has thus 
been evenly spread, the tube is immersed to the neck in ice-water, and 
then stored for future use. Some roll the tubes on ice, but the medium 
sets and hardens unevenly, in lumps, ridges, &c. — a condition of things 
likely to vitiate the count. In making a comparative determination a 
series of tubes are taken, a given quantity of the material under examina- 
tion put into each one, “ swashed ” about and the surplus thrown out, or 
by means of gentle heat (not, however, always advisable) incorporated 
with the medium. At the end of a given number of hours or days a 
count is made, the count repeated at intervals, the results recorded, and, 
if it is desired to experiment further, a cultivation begun. 
At this stage of the examination the counter (fig. 76) comes into play. 
It is simply a small Microscope adapted to tube examinations, and consists 
of a modification of a brass knife-clamp that grasps the tube, holding it 
firmly to the under side of the stage, the opening in which contains a 
cover-glass divided into square millimetres, or, in a more recent and better 
form, an opening in the stage 1 X I mm., and the greater diameter 
running lengthwise with the tube. The optical part is an *• Excelsior ” 
triplet, the lenses of which can be used separately or in combination ; 
the adjustment is frictional. The substage has universal movements, 
and may be readily detached if windo#- or lamp-light is preferred direct. 
The Bausch and Lomb Optical Company make the instrument.” 
Filtration and Sterilization of Organic Fluids by means of liquid 
carbonic acid.* — M. A. d’Arsonval describes a quite simple instrument 
for the cold-filtering and sterilizing of liquids containing colloid or 
albuminoid substances. A wrought-iron bottle filled with liquid car- 
bonic acid is connected by means of a narrow tube with a steel or copper 
cylinder which is to receive the fluid to be filtered. The receiver of 
course contains a porcelain filter, and this is easily removable for the 
purpose of cleaning or sterilizing. 
In practice the pressure used is about 45 atmospheres, and this is 
found to be quite as efficacious in many cases as sterilizing by heat. 
The effect of this method may be increased by combining a tempera- 
ture of 40° with the pressure, and, by certain modifications, cultivations 
may be attenuated or their development retarded. 
The author noticed that the richness of the filtrate in colloid sub- 
stances was in close relation to the pressure, and that in mixtures con- 
taining various ferments, for example, pancreatic fluid, the action of the 
fluids obtaiued by filtration varied with the different pressures. 
D’Arsonval’s Apparatus for maintaining a Fixed Temperature.! — 
M. A. d’Arsonval has invented a new thermostat, the temperature of 
which is regulated by quite a new device. The apparatus, intended 
chiefly for embryological and cultivation purposes, consists of a double- 
walled case, the interior of which is filled with water. At the middle 
* Comptes Rendus, cxii. (1891) pp. 667-9 (1 fig.). 
t Arch, de Physiol. Norm, et Pathol., ii. (1890) pp. 83-8, See Zeitschr. f. Wiss. 
Mikr., viii. (1891 ) pp. 102-4. 
