SCIENTIFIC SUMMARY. 
121 
best knovm of blistering media, the Spanish fly. The tincture of ranunculus 
lasts for a longer period than the cantharides preparation, and this fact, 
coupled mth the absence of injurious effect on the kidney, render it probable 
that ere long we shall see the buttercup frequently employed in medicine. It is 
often advisable to apply a blister to the loms in cases of congestion of the 
kidney, but cantharides cannot be employed for the purpose, because of their 
tendency to be absorbed, and produce violent inflammation of the urinary 
organs. 
How to photograph the Fundus Oculi.—lii the last number of the Ophthalmic 
Review we find a description of a very simple apparatus to be employed in 
photographing the interior of the eye. The instrument is described by 
Mr. Rosebmgh, of Toronto, and is of his invention. The eye is illuminated 
by solar light reflected from plate-glass ; and a sufficient number of the rays 
of light reflected from the fundus of the eye pass through the plate-glass to 
form a highly, almost brilliantly-illuminated image of the fundus, in or near 
the principal focus of a convex lens, placed behind the plate-glass, and of any 
focal length, from one to eight or ten inches. The tube containing the plate- 
glass has a second tube attached to its side, and placed at right angles, and 
through this the light falls from the sun ; the first tube has one extremity 
adapted to the eye to be photographed and the other fitted to a small camera, 
upon the plate of which a very perfect image is formed. Altogether the 
instrument is a most ingeniously constructed one, and must be a great im- 
provement upon the double ophthalmoscope used as an apparatus in photo- 
graphing the fundus oculi. 
Animal Mechanics. — Under this title we find a most important paper from 
the pen of the Rev. S. Haughton, M.D., F.R.S., in the last issue of the Dublin 
Quarterly J ournal of Science. He has worked out the question of the me- 
chanical forces of muscles, their duration when in operation, and their value^ 
with the most wonderful degree of minuteness, considering the vague nature 
of the subject. He lays down the two following principles, or rather postu- 
lates, as he terms them : — 
1st. The amount of work done by a given muscle in a given time is propor- 
tional to its weight, that is, to the number of muscular fibres in contraction. 
2nd. The mean lengths of the different muscles employed at each point are 
proportional to the perpendiculars let fall from the centre of motion of the 
joint upon the direction in which the muscles act. 
He considers that the 2nd postulate is supported by these three consider- 
ations : (1) The distance through which the point of application of a muscle is 
moved by its contraction, is proportional to the mean length of the muscle. 
(2) It is geometrically evident that the perpendiculars let fall on the direc- 
tions of the muscles, are proportional to the species moved through by their 
points of application. (3) The Divine contriver of the joint has made a perfect 
mechanism, and therefore employs a minimum expenditure of force. 
Suture of the Median Nerve. — This operation has lately been performed by 
M. Laugier, and with the most successful results. In the first instance the 
patient lost all sensation in the thumb and two adjacent fingers ; upon the 
evening of the operation, sensibility began to be restored and became even 
more marked on the succeding day, and after a few days it was entirely 
restored. Hence M. Laugier concludes : — 
