1Y8 



THE AMERICAN MONTHLY 



[September, 



forms to diseases, the disinfection of 

 clothes and effects, contributions to 

 morphology, and a critical and ex- 

 perimental consideration of the con- 

 stancy of pathogenic forms. 



CORRESPONDENCE. 



To THE Editor. — E. P., who in- 

 quired in July about mounting plant- 

 hairs and fungi, will find balsam a 

 satisfactory medium for all such objects 

 as are rather hard, and contain but little 

 water, but all the more, delicate parts of 

 plants, and small fungi, require a watery 

 medium to make the best preparation, 

 glycerin-jelly prepared to be fluid at com- 

 mon temperatures but stiff at 45" F., is, 

 next to balsam, the most convenient and 

 useful medium, if used as follows : The 

 object, if not already soaked in glycerin 

 or in a thin jelly long enough to be satur- 

 ated, should be arranged on the slide, and 

 covered with the jelly a short time before 

 the cover-glass is put on, then, if warmed 

 gently on the hot plate, or over a lamp 

 till the jelly is very fluid, all air bubbles 

 will pass out without the slightest difficul- 

 ty. Allow the sHde to cool, and if there 

 is a large surplus of jelly, remove it with 

 a knife, or a scraper, then hold the 

 slide under the top of a water-cooler, 

 which sets the cover on so that with a 

 camel-hair brush, every smear may be 

 removed while the water is running, leav- 

 ing a clean edge ; then dry and run a 

 balsam ring over the edge of the cover, 

 and the slide will be permanent. All 

 preparations mounted in watery mediums 

 not hermetically sealed from the air by a 

 resinous or non -volatile covering, will 

 spoil by evaporation. 



W. H. Seaman. 



NOTES. 



— Probably some of the finest prepara- 

 tions of embryo chicks that can be found 

 are made by Mr. J. Lee Smith, of this 

 city. Some of his slides seem to be abso- 

 lutely perfect. He has been at work on 

 the preparations for a long time, and 

 although we thought he was remarkably 

 successful a year ago, the slides he now 

 makes are much superior to his former 

 ones. Yet he says we have not seen his 

 best ! We are not aware whether the 

 slides can be purchased, but if not, we 



hope they will be placed on sale ; for they 

 should become known to microscopists 

 throughout the country. 



— Mr. Crisp described a " Jumbo " mi- 

 croscope, at the Royal Microscopical 

 Society some time ago. It stood 4 feet 

 high, had a tube 4 inches in diameter, 

 and weighed 1}4 cwt. It was made about 

 fifty years ago. How such a stand would 

 delight Mr. Stodder ! 



— Mr. P. M^gnin has drawn attention 

 to the liability of mistaking other encysted 

 worms for Trichina spiralis. Care 

 should be taken by all who have occasion 

 to examme encysted worms in man or the 

 the lower animals, to make out their 

 forms and peculiarities ; for not all en- 

 cysted and coiled up worms are trichinae. 



— Mr. T. W. Engelmann has carried 

 out some experiments on bacteria and • 

 spirillas, which lead to the somewhat re- 

 markable conclusion, that certain spirillas 

 may derive sufficient oxygen to support 

 life from certain greenish bacteria, which 

 disengage that gas. 



— Mr. A. D. Michael, states that to ob- 

 tain the best effects with polarized light 

 on a dark ground, objects should be 

 mounted in glycerin. In this he is not 

 fully supported by the opinions of other 

 observers ; but probably the same objects 

 were not compared, Usually balsam is 

 preferable for polarized light, but some 

 detail is sure to be lost when delicate 

 objects are mounted in balsam. Mr. 

 Michael seems to allude particularly to 

 vegetable tissues when he recommends 

 glycerin. 



— A method of preparing minute ento- 

 mostraca, such as water fleas, but also 

 apphcable to other small animals, such as 

 mites and spiders, was recently described 

 by Mr. M. M. Hartog, before the Royal 

 Microscopical Society (London). In out- 

 line, the process was as follows : — 



The specimens were killed by adding 

 a few drops of osmic acid X.Q the water, 

 when they fell to the bottom they were 

 taken up and placed in alcohol of 30 per 

 cent., from which they were transferred 

 to alcohol of 50 per cent., then to cochineal 

 solution in 70 per cent, alcohol, then 

 washed repeatedly in 70 per cent, alcohol, 

 then placed in 90 per cent, and finally 

 in absolute alcohol. Then a small quantity 

 of oil of cloves was poured in the alcohol, 

 and at the line of juncture of the two 

 liquids, the specimens became permeated 

 with the oil. They were then imbedded 



