ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 541 



for the purpose of injection ; fresh water may also be used for some 

 marine species. A leech, for example, is placed in water containing 

 a small quantity of chloroform ; after a few moments it sinks to the 

 bottom and remains motionless. It should be allowed to remain in 

 the water for one or two days before attempting to inject it. 



The simplest and most convenient form of syringe consists of a 

 glass tube drawn to a fine point at one extremity, and furnished at 

 the other with a rubber tube. Preparatory to injecting, the glass 

 should be plunged in warm water for a few moments ; then, after 

 expelling the water, it may be filled with the injection-mass by sucking 

 the air from the rubber tube. If the injection-mass is turned into 

 the large end of the glass, it may happen that granules are introduced 

 which are large enough to obstruct the narrow passage of the small 

 end. After inserting the cannular end in the vessel, clasp both with 

 the forceps, and then force the injecting fluid, by aspiration through 

 the rubber tube, which is held in the mouth. When the operation is 

 completed, place the animal in cold water, in order to stiffen the 

 injected mass. 



Anilin Staining.* — Dr. Bareggi, in order to render more perma- 

 nent preparations stained with anilin colours, proposes to merely 

 cover the section, &c., with Canada balsam dissolved in chloroform, 

 and to allow the balsam to dry slowly, no cover-glass being used. 



When working with dry or with water immersion lenses, such 

 preparations can be examined without detriment, as water is not 

 miscible with balsam. But when working with oil-immersion lenses 

 and with cedar oil, which dissolves balsam, it is necessary to be 

 careful during the examination. 



It would perhaps be preferable to use instead of cedar oil the 

 salt solutions which have been proposed for this purpose, or the 

 solution of chloral hydrate in glycerin, or still better, the solution of 

 zinc iodide in glycerin. 



Chrome Alum in Microscopical Technique.f — Dr. G. Martinotti, 

 from a consideration of the behaviour of potash alum which is a pro- 

 minent constituent of certain stains (carmine, haematoxylin, &c.), 

 wished to make some experiments with ammonia and chrome alums. 

 The results from the use of ammonia alum were not encouraging, 

 but by substituting chrome alum or the double sulphate of potassium 

 and chromium for potash alum he obtained sufficiently satisfactory 

 results. 



Chrome alum is isomorphous with potash alum and crystallizes 

 in dark violet octahedra soluble in water, but insoluble in alcohol. 

 If the watery solution be heated above 80° (1 the violet colour turns 

 to a green, and this hue is retained on cooling. Carmine chromate 

 is prepared by boiling 10 parts cochineal in 500 parts water and 

 adding 1 part chrome alum, filtering while hot and then allowing it 

 to stand. The residue is carefully washed and dried at a temperature 

 not exceeding 30° C. It is easily soluble in ammonia, and possesses 



* Gazzetta degli Ospitali, 1884, p. 645. 



t Zeitschr. f. Wiss. Mikr., i. (1884) pp. 361-6. 



