280 
NOTES AND MEMORANDA. 
[Monthly Microscopical 
Journal, Nov. 1, 1869. 
Photographing Diatoms. — The ' British Journal of Photography,' 
in replying to a correspondent, suggests that he should avoid diffi- 
cult subjects ; at first it would be much better to try such an object 
as Pleurosigma Utt'orale, which contains 24,000 lines to the inch, 
than the P. macrum, which contains 85,000, and would require an 
objective of y^g^th of an inch to show the markings. The former is 
within the range of a good ^-inch power, the latter could not be 
seen by it. 
Polarizing Crystals from Logwood. — At the concluding sessional 
meeting of the Literary and Philosophical Society of Manchester, 
Mr. Dancer stated that he had received from Mr. Eichard Dale, Corn- 
brook, some Hsematoxylin — the source of the colouring properties of 
logwood. From the appearance of the crystals Mr. Dale expected 
they would form a polarizing object, and Mr. Dancer found that 
opinion to be correct. Mounted slides of the crystals from an alco- 
holic solution were exhibited to the meeting by polarized light ; they 
are quite equal to Salic in in intensity of colour, and do not require 
the aid of a selenite stage. They form a welcome addition to the list 
of polarizing objects. 
Milk of diseased Cows under the Microscope. — In the ' Lancet ' 
of October 23rd, Professor Brown has given an account of his ob- 
servations on the milk of cows suffering from the " foot and mouth 
disease." He has given numerous illustrations of specimens seen 
under high powers, and showing the presence of Bacteria and allied 
vegetable forms in abundance. The details will be found in our 
summary of " Progress." 
The Microscope attacked and defended in Paris. — A great battle 
has been taking place in the French journals between two well-known 
savants. M. Nelaton, surgeon and senator, contended that the micro- 
scope is valueless in medicine, and that it often leads to mistaken 
diagnosis. But his assertions have not passed unchallenged, for M. 
Verneuil has given him a pointed reply in the columns of the ' Gazette 
Hebdomadaire.' After having stated what great results the micro- 
scope has afforded in the hands of such men as Robin, Broca, Lebert, 
Davaine, Yirchow, KoUiker, and others, and after having mentioned 
that it had now become the indispensable complement of anatomical 
research in the dead-room, throwing a brilliant light on the origin, 
the evolution, and the transformation of those innumerable lesions 
which destroy man, M. Verneuil asked M.- Nelaton whether he be- 
lieves that all surgical science may be acquired in the ward of an 
hospital. If not, and if, on the contrary, he (M. Nelaton) admits the 
assistance of the accessory sciences, if he makes use of chemical 
agents and of physical instruments, if he practises vivisections, if he 
utilizes statistics, if he consults J. L. Petit, Scarpa, Langen, and 
Syme, why should he disdain the microscope ? " For if it is good to 
diagnosticate stone by the aid of a sound, polypi with the laryngo- 
scope, an amaurosis with the ophthalmoscope, paralysis by means of an 
electric machine, diabetes with potash, why reject the lens for recog- 
nizing leucocythsemia or spermatorrhoea ? " 
