SCIENTIFIC SUMMARY. 
223 
are kept half closed, and a feeling of obstruction in the frontal region. The 
second is characterised by diplopia, dilatation of the pupils, and subsequent 
heaviness of the head, tending to sleep and drowsiness. The second effects 
are produced by doses of from 5 to 9 centigrammes, and the first by doses of 
from 10 to 135 milligrammes. 
Influence of Respiration on the Circulation. — Dr. Burdon-Sanderson, who 
delivered the Croonian Lecture at the Royal Society on March 7, put 
forward opinions relative to the influence of the respiratory movements over 
the movement of the blood in the great vessels, which are different from 
those stated in most of the existing text-books on physiology. Dr. San- 
derson stated that so long as the air passages are open, each expansion of 
the chest is followed by increase of arterial tension, so that the effect of 
inspiration is to increase alike the pace and frequency of the heart’s contrac- 
tion. When, however, the respiratory apertures are closed, as in suffoca- 
tion, the relations are reversed, the pressure in the arterial system being 
then highest in expiration, and vice versa. 
MICROSCOPY. 
A Diaphragm Eye-piece. — This ingenious and .useful contrivance, the 
invention of Henry J. Slack, Esq., F.G.S., has been lately described to the 
Microscopical Society. Mr. Slack found that in viewing small objects by 
transmitted light, it frequently happens that there is such a large field of 
light external to the object, that not only are small details of structure 
obscured, but the eye is wearied by the influence of the luminous stream. To 
prevent this he requested Mr. Ross to adjust four movable shutters, so 
that an A eye-piece might be susceptible of all the changes in the form and 
size of its field that different objects would require. This change was soon 
effected. Mr. Slack has, therefore, provided microscopists with an eye- 
piece which will be found useful in research, and will tend to protect the 
eye from the injurious influence of the stream of bright light which usually 
falls upon it. 
Wire-spring Clip. — Those who have used Dr. Maddox’s wire-spring clip 
will be glad to learn that an improved form of it was exhibited by Mr. 
Jabez Hogg some time since, at a meeting of the Microscopical Society. 
It differs from the original form in having the point, which presses on the 
covering-glass, protected by a little disc of leather. The advantages of this 
addition are manifold. The pressure of the spring is distributed uni- 
formly over the covering-glass, and this latter is therefore not only less 
likely to be broken, but less liable to disturbance from its proper position. 
They are sold by all makers. Those we have seen were shown us by Mr. 
Charles Collins. 
The Amateur's 11 Mounting ” Case. — This is a case prepared by Mr. 
Collins, of Great Titchfield Street, and of which we give an illustration. 
It is intended for the use of those whose microscopic pursuits are of a 
general character, and is, so far as we can see, admirably adapted to the 
