680 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of the air, but protected from the dust by a large watch-glass. The 
preparation may be examined from time to time under a low power to 
see how the staining is getting on. The effect varies extremely : thus 
the endings of motor nerves stain in 5-10 minutes, while the nerves 
in the retina require two or three hours or even longer. 
As the staining disappears in a comparatively short time, it becomes 
necessary to fix the pigment. For this purpose picrate of ammonia is 
advised. This saturated aqueous solution precipitates the methylen- 
blue in a finely granular condition, rendering the rest of the tissue highly 
transparent. The length of time required for fixing the stain varies of 
course with the thickness of the tissue ; some specimens are fixed in 
20 minutes, while others require as long as 12 hours. The preparations 
are then mounted and examined in a mixture of equal parts of glycerin 
and distilled water. 
Preparations which have been stained with methylen-blue may be 
hardened by immersion for 2-3 hours in a saturated spirituous solution 
of picrate of ammonia and then, having been imbedded in elder-pith or 
liver, sectioned with a razor. The sections are placed in glycerin. Or 
the stained tissue may be frozen and then sectioned. 
By the foregoing method the author has obtained very excellent 
results, judging from the illustrations which accompany the text, from 
muscles of Amphibia and Reptilia. The procedure is less complicated 
than that where the stainings are obtained by injecting the vascular 
system with a solution of methylen-blue. 
(5) Mounting", including Slides, Preservative Fluids, &c. 
Arranging Diatoms.* — Mr. Cunningham states that he arranges 
selected diatoms by transferring directly from a strewn slide to the 
exhibiting slide by the aid of a “ Kain’s mechanical finger ” attached to 
a Beck’s 1/2-in. objective, the slide being manipulated by the left 
hand, and the bristle being directed into the field from the left-hand 
side. This method, he says, counteracts the effect of reversal of image, 
enabling every desired movement to be accomplished with ease and 
certainty. The right hand assists in racking the diatom from the slide 
high enough to clear the edge of the cover-glass upon which the diatoms 
are to be fixed. Very minute species are selected and isolated by this 
means. 
New Mounting Dammar. f — A very superior mounting medium was 
accidentally discovered by adding by mistake liquor potassae to a thick 
solution of benzol-dammar. After the lapse of some months, the jar, 
with a beautifully clear zone of some sort of gummy material super- 
imposed upon a white one, was discovered. The clear zone, some 
6 ounces, was drawn off and tested as to drying and other properties. 
It was found that it dried slowly, but ultimately set very firmly. Placed 
on a slide heated to a point that instantly vaporized water, it dried 
without forming a bubble. Used as a mounting medium on a hot slide, 
no bubbles were formed, and while in bulk the colour is somewhat 
darker than Canada balsam, in ordinarily thick mounts it is almost 
imperceptible. 
* Journ. N.Y. Micr. Soc., vi. (1890) p. 60. 
t St. Louis Med. and Surg. Journ., Iviii. (1890) p. 37. 
