to 
to 
NATURE 
[Marcu 7, 1912 
balls contained in the metal vessel and the interior 
surface of the same. It is evident that if the weight, 
Kk, were not on the central cone, as shown, or unless 
some similar method were adopted to control the 
cone to prevent it from rotating, no grinding action 
would result; the central cone, in fact, must either 
remain still or be allowed to rotate at a slower speed 
than the containing vessel. The metal weight, K, is 
of such size that on the whole machine being driven 
at a suitable speed the action of gravity results in 
the steel cone remaining still, and so a grinding 
action takes place between the steel balls and the 
inside surface of the containing vessel. To bring the 
bacterial or other cells under the grinding action of 
the balls, the speed of rotation should be from 1000 
to 1500 revolutions per minute; centrifugal action is 
then sufficient to ensure that the whole of the material 
does actually come between the balls and the metal 
vessel. ; 
The method of using the machine is briefly as fol- 
lows :—The bacteria, after being removed from the 
‘culture tubes or plates on which they are grown, are 
ccentrifugalised; the semi-fluid mass is then emulsified 
with saline solution, so that it is of a creamy con- 
sistence. This material is then introduced into the 
container by means of a pipette through the hollow 
centre of the steel cone. This ensures that no parts 
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of the machine are disturbec more than is absoluely 
necessary either before or after grinding. The 
machine is then run for a longer or shorter period, 
depending on the amount of material to be dealt with, 
and the ground material is then pipetted off through 
the central steel cone. As the balls are themselves free 
to rotate, the amount of friction is negligible, but any 
rise of temperature may be prevented by allowing a 
small stream of carbonic acid gas from a cylinder 
of liquid carbonic acid to impinge on to the side of 
the vessel; alternatively an ether spray, such as is 
used for section-cutting purposes, may be used, and 
will be found quite efficient. 
The vertical type of machine (Fig. 2) is exactly 
similar in all essential details, except that the central 
steel cone is controlled by means of electromagnets. 
Oi the top of the cone a mass of soft iron is fixed, 
and this is kept from rotating by means of the elect-5- | 
magnets, J. The only constructional difference is that 
the containing cylinder, F, is made of vulcanite, so 
that it is perfectly diamagnetic. The chief advantage 
of this design over the one previously described is 
that it can be completely covered by a glass bell-jar 
while in action. A bactericidal agent may be placed in 
the groove O, and the bottom edge of a_bell-jar 
allowed to dip into it. 
NO. 2210, VOL. 89] 
The etfect of disintegrating yeast cells for ten and 
fifteen minutes is seen in Figs. 4 and 5 respectively, 
Fig. 3 showing the cells before the commencement of 
the process. It is interesting to note that in Fig. 5 
the cell contents have taken up the stain which was 
used in making the microscopical preparation, whereas 
the cell envelopes remain unstained and show as clear 
areas, thus demonstrating that the cell contents have 
been completely expressed. J. E. Barnarp. 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
CampripGE.—Mr. E. A. Newell Arber, of Trinity 
College, has been approved by the general board of 
studies for the degree of doctor of science. 
The general board of studies has issued an 
important report on advanced students, of which there 
are at present two classes: (1) those who qualify for 
a degree by submitting a dissertation approved by a 
degree committee of a special board, and (2) those 
who qualify for a degree by reaching a certain speci- 
fied standard in a tripos examination. The board 
points out that there is considerable variation in the 
standard required of advanced students in the various 
tripos examinations. 
The number of advanced students of the latter class 
admitted to courses of study in the fourteen years 
from 1896 to 1909 inclusive was 1o1. In the same 
period eight applications were refused. Of the ror 
admitted, 35 reached the standard required in their 
respective tripos examinations; 18 were rejected; 48 
did not present themselves for examination. These 
statistics point to the conclusion that a good many 
students are admitted to the status of advanced 
students who have no real claim to the distinction 
which such admission may be held to confer. 
After full consideration of the working of the pre- 
sent regulations, the general board has come to the 
conclusion that it is desirable that advanced students 
should no longer be admitted to courses of advanced 
study, but that they should be admitted to courses of 
research only. 
With this end in view, the board proposes that the 
class of affiliated students should be enlarged, and 
that affiliated students should not only be permitted 
to proceed to a degree after residing in the University 
for six terms, but in the case of certain tripos ex- 
aminations should be also admitted to the second part 
without necessarily having fulfilled the ordinary con- 
dition of having previously passed in the first part of 
the tripos or in some other tripos. 
