278 
NOTES AND MEMORANDA. 
toplasm becomes purple. In many instances where carmine has given 
but indifferent results, haematoxylin will be found to succeed most 
admirably. As to the stability of the colouring, I need only remark 
that specimens tinted and mounted in December, 1869, show as per- 
fectly as when first put up. 
Nitrate of Silver in the Examination of Tissues. — Col. Dr. Wood- 
ward states that a solution of one part of chemically-pure nitrate of 
silver in four hundred parts of distilled water (by weight) is perhaps 
most generally useful, though stronger solutions may be needed for 
special cases. The bottle should be covered with yellow paper to ex- 
clude the light. For the investigation of the serous membranes and 
other large epithelial surfaces, it is merely necessary to pour a little 
of the solution upon the piece selected for examination, or to brush 
the surface lightly with a camel’s-hair pencil dipped in the reagent. 
The piece is then thoroughly washed with distilled water and exposed 
to the light, preferably to the direct rays of the sun. To obtain the 
best effects, the tissue should be taken just after death, or at least 
should be as fresh as possible. It should be laid in a little distilled 
water, in pure glycerine, or in alcohol, during its exposure to the sun- 
light. The result may be regarded as satisfactory if, after a few 
minutes’ exposure, the boundaries of the cells are everywhere mapped 
out with delicate black lines without other visible black deposits, 
either on the surface or in the substance of the tissue. If the same 
solution is injected into the blood-vessels or the lymphatic trunks, a 
similar effect is produced, provided the parts are sufficiently thin and 
transparent to permit a prompt exposure to the light. The urinary 
bladder, mesentery, lungs, lymph- sacs, skin, and other parts of the 
frog offer excellent materials for this method. The blood-vessels, how- 
ever, are apt to contract irregularly when thus injected just after death, 
and for the display of their endothelium it is perhaps best to employ 
the solution of gelatine and silver described by Dr. N. Chrzonszczewsky, 
of Charcow. Half an ounce of fine gelatine is dissolved in four ounces 
of distilled water, and to this is added a solution of one scruple of 
nitrate of silver in two fluid-drachms of distilled water. This fluid is 
to be injected warm, like any other injection-fluid containing gelatine. 
The syringe should be of silver, or of hard rubber with a silver nozzle. 
The precise quantity of gelatine must vary somewhat with its quality, 
the point being to use a fluid which will gelatinize handsomely when 
cold ; the vessels are thus kept handsomely distended, and are con- 
sequently better suited for examination under the microscope. 
