162 



THE AMERICAN MONTHLY 



[September, 



to the best avantage, although I 

 have not often been able to better 

 the arrangement which the insect 

 has spontaneously assumed in the 

 acid. Insects that have been pre- 

 served in alcohol will be cleared in 

 tlie acid, but slowly and without 

 wholly losing the stiffness and con- 

 tracted shape assumed in the alcohol, 

 to which fluid the acid seems to be 

 repugnant, as it is inclined to run 

 into drops when an alcoholic speci- 

 men is placed iii it. 



If the microscopist, when he goes 

 on a collecting trip, will take along 

 a small, wide-mouthed bottle of 

 acid and drop into it the small in- 

 sects he meets, he will, on his return 

 home, find a rich harvest that will 

 occupy his eyes and hands for many 

 an hour. He can examine his 

 treasures and mount them at once, 

 or return them to the acid to await 

 his leisure. I can discover no dif- 

 ference between the effects of im- 

 mersion for a few minutes and im- 

 mersion for weeks. 



Heat applied to the acid hastens 

 its action, but I do not see that it 

 intensifies it and for my own part I 

 prefer to let the acid act on small 

 insects without heat, and watch the 

 progress of its slow action as it 

 clears up and discloses one feature 

 after another. 



In using dammar I have not had 

 such good success as with balsam 

 for in some cases a milky line ap- 

 peared at the edge of the wave of 

 dammar, which made it necessary to 

 apply more of the medium than 

 was required for the mount so 

 as to drive this milkiness out beyond 

 the cover, leaving a surplus to be 

 afterwards cleaned off, but I have 

 made some good dammar mounts, and 

 think the difficulty can be obviated 

 although I have not had time to ex- 

 periment with it to determine this. 



On injected tissues the acid works 

 well, so far as to show the injected 



vessels, but renders everything else 

 so transparent and glass-like, as to 

 show no structure with any satis- 

 faction. I leam from Dr. Blasdale 

 that he had long ago tried the acid 

 on injected specimens, and rejected 

 it, on account of the too great trans- 

 parency and indistinguishableness 

 communicated to the tissue bearing 

 the injected vessels. 



The writer in Science Gossip 

 states that vegetable tissues are 

 acted on by the acid equally as well 

 as animal tissues, but I have not 

 tried it myself on vegetable pre- 

 parations. The same writer refers 

 to a communication by liimself on 

 the subject, written several years 

 ago, but it must have met with 

 limited notice, for I have not yet 

 met with any one who ever saw it, 

 or who was aware of the availability 

 of the acid for this purpose, except- 

 ing Dr. Blasdale, hence I have 

 thought it worth while to give the 

 hint to your readers, to many of 

 whom it is probably new. 



o 



The New *^ Congress " Turn- 

 table. 



The "Congress" Turn-table, in- 

 vented and first exhibited by me at 

 the " Congress of Microscopists " 

 held at Indianapolis, may be thus 

 briefly described. 



Into the upper surface of the ro- 

 tating plate, diametrically opposite 

 and equidistant from the centre, 

 two circular plates or discs, one inch 

 in diameter, are set, their sufaces 

 flush with that of the large plate. 

 Pivots from the two discs project 

 through the plate, and each carries 

 upon the lower side of the plate 

 a toothed-wheel. A hollow sleeve 

 rotating freely upon the stem of the 

 table carries a third and larger 

 wheel, which gears into the two 

 others and thereby gives rotation to 

 the discs in the top of the plate. 



Near the opposite edges of the 



