NOTES AND MEMORANDA. 465 



Searching for TrichinaB. — Mr. George W. Morehouse, of Way- 

 land, N.y., says * that it is undeniahle that microscopists waste a 

 good deal of valuable time by the use of higher powers than are 

 necessary, and by imperfect preparation of objects for examination. 

 In nothing is this more forcibly illustrated than in the examination 

 of pork for trichinae. For this purpose it is customary to use powers 

 of 75 diameters and upwards (seldom as low as 50), and the meat is 

 not always made sufficiently transparent for ready detection of the 

 parasites. A power of 25 diameters, obtained with a good 2-inch 

 objective, and 2-inch ocular, is amply sufficient. With the 2 inch 

 we have greater depth of focus, the object is still shown with great 

 clearness, and, most important of all, we are able to do as much 

 searching in one hour as it would take about nine hours to accom- 

 plish with a g-inch objective. 



As to preparing pork for present, rapid, and accurate observation, he 

 has found the following method to work well : — Cut thin longitudinal 

 sections from the extremities of muscles, and from other favourite 

 localities where the worms, in migrating, stop in greatest abund- 

 ance, and place the sections in a ^vatch-glass, covering them with 

 acetic acid. In a few minutes the tissues will be transparent enough 

 to enable one to see the letters through the specimens when the 

 watch-glass is placed on a printed page. Drain off the acid, add 

 water and examine, or wash and transfer to a glass slip (large, with 

 large cover, for a number of sections at once), either in water 

 or glycerine, and cover. For permanent preservation, while the 

 sections are still in glycerine, press them for several days between 

 plates of glass, and mount at leisure in pure glycerine. When thus 

 prepared, the parasites remain coloured more highly than the sur- 

 rounding muscular fibres, and readily attract the eye. They are so 

 plain, that none, when brought into the field of view, can escape 

 instant detection. The process is simple, takes but little time, and 

 is inexpensive. 



Method of Studying the Structure of Vegetable Matter.— 

 M. Merget, of Bordeaux, finding that mercurial vapour easily per- 

 meates disks of wood, recommends it as a means for studying the 

 structure of vegetable matter. If wood, after exposure to the vapours 

 of mercury, is brought in contact with a sensitive paper (obtained by 

 saturating paper with an ammoniacal solution of nitrate of silver) a 

 distinct design of the fibro-vascular bundles and of the medullary rays 

 will be obtained. We may thus design the stomata of a leaf, and show 

 that in the case of those possessing stomata on both surfaces the air 

 circulates from one epidermis to the other.f 



Thin Stages. — It is, we think, a matter for surprise that with all 

 the attempts that have been made to produce stages of excessive thin- 

 ness, to allow of the use of light of extreme obliquity, opticians have 

 never provided their Microscoijes with any contrivance for allowing 

 the slide to be attached to the under side of the stage. Such a con- 

 trivance would cost a very trifling sum, and by its adoption the 



* 'Am. Journ. Micr.,' iv. (1879) .30. f 'M. Journ. Sci.,' i. (1879) 389. 



TOL. II. 2 H 



