1046 SUMMARY OF CURRENT RESEARCHES RELATING TO 



others take up too mucli. Haller recommends boiling the mites, &c., in a 

 mixture of aq. dest. and potash (2 : 1) and then mounting the chitinous 

 framework of the head in glycerin slightly dilute, while Ehlers treated 

 them with ammonia and oil of cloves, but the author had no success with 

 either of these methods. 



The structure of the tracheae is best shown by slight staining with 

 picrocarmine, illuminated by Abbe's condenser with central stop. 



Sections of stained mites and ticks are prepared by immersing them in 

 gelatin and hardening in alcohol. They are then imbedded in elder pith 

 and so sectioned. Ova should be examined in dilute salt solution (glycerin 

 swells their capsule too much) and without a cover-glass. Picrocarmine 

 stains ova very well and clearly brings out the segmentation, which if 

 unstained, and in glycerin does not appear. 



Preparation of Microscopical Parasites.* — ^Dr. Stoss obtains his pre- 

 parations of Acarid^ by scraping off the scabs from the diseased anijual 

 and softening them in a 10 per cent, potash solution for half an hour. A 

 little piece of the softened scab is then mixed with a drop of water and 

 examined carefully under a low power ( X 90). A suitable Acarus having 

 been discovered, it is removed from the action of the potash solution by 

 pushing the slide to the right and the cover-glass to the left with a needle. 

 The Acarus is then freed from all extraneous objects and left on the slide 

 for mounting, or is transferred to a watchglass containing glycerin by 

 means of a needle. The fluid, which is suitable for extracting the 

 potash lye, for preventing the Acarus from drying, or for preserving the 

 animal, consists of a mixture of equal parts of 90 per cent, spirit, glycerin, 

 and water. The Acarus, immersed in a drop of this fluid, is sealed up with 

 a rim of wax, paraffin, or asphalt run round the cover-glass, but dammar 

 or Canada balsam dissolved in chloroform or xylol are probably better and 

 more durable. 



When the Acari exist in quantity among the scabs and scales, and there 

 is no difficulty in obtaining a good specimen, as, for example, is usually 

 the case in cat's mange, the following procedure is recommended : — The 

 scales are put for some time in the potash solution, and are then washed in 

 distilled water several times. The Acari and scales are allowed to settle at 

 the bottom of the vessel, and the supernatant fluid decanted off. The 

 glycerin-spirit mixture is then poured over them, and in this they may be 

 kept for an indefinite period without undergoing any change. 



Psorosperms are well preserved in the glycerin-spirit mixture, but the 

 proportions are different (1 — 1 — 2 water). And it is noticeable that dif- 

 ferent objects require slight alterations in the quantities of the constituents 

 in order to produce an equilibrium between the contracting action of the 

 spirit and the swelling action of the glycerin. Thus Oxyuris mastigodes 

 remains quite intact in a fluid of 1 — 1 — 2, while Filaria shows fine surface- 

 creasings, which do not appear with a little more water. 



Although these parasites keep very well by the foregoing methods, they 

 are extremely susceptible of mechanical injury. Damage from this cause is 

 avoided by mounting in glycerin jelly. This medium is produced by 

 softening gelatin by leaving it all night in water. It is then cut up and 

 fluidified in a water-bath without the addition of water, and mixed with 

 10 per cent, glycerin and 1 per cent, carbolic acid. When cold the 

 mass is cut up and kept in stoppered bottles. A mite or tick is mounted 

 by placing small bits round it on a slide and then warming gently over a 



* Deutsche Zeitschr. f. Thiermed. ii. Vergl. Tathol., xii. (1887) pp. 202-5. 



