ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 515 



long and 1 cm. in diameter. In a few hours the expressed jelly may he 

 scraped off with a knife, the last traces being removed with lukewarm 

 water. The slide is then cleared up with spirit and ringed round with 

 some cement. Glycerin jelly not only possesses the clarifying property 

 of glycerin, but all the other advantages of this medium. 



Haensell, P. — La Methode de i'inclusion du Globe Oculaire dans la paraffine et 

 dans la celloidine. ( Method of imbedding the eye in paraffin and celloidin.) 



Bull. Clin. Nat. Ophthalm. Hop. Quinze-Vingt, IV. (1886) p. 154. 

 Reynolds, R. N. — A new Planisher. 



The Microscope, VIII. (1SS8) pp. 104-5 (4 figs.). 



(4) Staining' and Injecting-. 



Staining Living Preparations.* — Prof. M. Flesch is of opinion 

 that living objects do not become stained by the ordinary methods, or do 

 so in a way quite different from hardened preparations. Cyanin, for 

 example, produces in the tissue-elements of the living organism different 

 forms from those in which the same dye has been employed after fixa- 

 tion. "What has stained in the dead preparation can never be similarly 

 affected while alive. The parts which become stained show in many 

 cases a great chemical activity, a lively power of reduction towards 

 certain chemical compounds. One series of stains is only successful 

 after previous treatment of the object with easily reducible metallic 

 combinations. By control experiments it is seen that the staining ex- 

 tends just as far as the metallic precipitate. The original constituents of 

 the tissues are not stained, but chemical products which result from the 

 treatment with hardening agents. These might be metal albuminates 

 or decomposition products arising from the chemical processes at the 

 death of the living tissue, induced by the reduction processes. The 

 result of a stain can only be judged from the chemical processes arising 

 during fixation. 



Staining Nerve-endings with Methylen-blue.f — Dr. C. Arnstein 

 states that in frogs injected with methylen-blue the motor nerve-endings, 

 Courvoisier's fibres, and the cells of the sympathetic are stained. In 

 the freshly cut-out retina there is usually no stain, but this appears 

 after the air has acted upon it. As a fixative, besides the iodine pre- 

 viously given, picrocarmine or picrate of ammonia may be used. The 

 choice of the substance depends on whether a nuclear or diffuse stain 

 is desired. Fixation by the last two methods is more lasting than when 

 effected with iodine, though with the latter the nerves are deeply stained. 

 Mammals and birds die too quickly after the injection of the methylen- 

 blue for the method to be practically available, yet these animals, after 

 they have been killed with chloroform, can be successfully injected 

 through the heart or some large vessel. The pigment is used in a 

 concentrated form, and the injection is suspended directly the resistance 

 becomes marked. The organs first stained blue quickly become pale, and 

 no nerve-staining is seen at first, but this occurs directly there is access of 

 air to the preparation. The gradually occurring colour may be followed 

 under the Microscope, and when it has attained its maximum some drops 

 of a fixative medium may be added. In this way very perfect nerve- 

 endings from the cornea, iris, and retina of mammals and birds have been 



* MT. Naturforsch. Gesell. Bern, 1887, pp. xiv.-xv. 

 t Anat. Anzeig., ii. (1887) pp. 551-4. 



2 N 2 



