ZOOLOGrY AND BOTANY, MICROSCOPY, ETC. 275 



In the case of leeches and large species of earthworms, the natural 

 injection is made from the ventral sinus. In all cases a glass tube is 

 used, with a finely drawTi-out point. The injection is complete when 

 the injection issues from the counter-opening. 



Animals to be injected alive are kept quiet by cold (laying upon 

 ice). Besides the animals mentioned, large caterpillars, beetles, 

 Libellulid larvte, locusts, &c., have served as objects for injection ; 

 the glass cannula is introduced into the posterior end of the dorsal 

 vessel, and the counter-opening is made in the ventral vessel, and 

 vice versa. 



Cold Injection Mass.* — A. Wikszemski describes a modification of 

 Panseh's method : — Thirty parts by weight of flour and one of ver- 

 milion are mixed while dry, and then added to 15 parts by weight of 

 glycerine and subjected to a continuous stirring until of a homogeneous 

 viscous consistency ; then 2 parts of carbolic acid (dissolved in a little 

 spirit) are added to it, and finally 30 to 40 parts of water. This injec- 

 tion mass is specially adapted for subjects already injected with carbolic 

 acid (in the proportion of 1^^ part by weight each of carbolic acid, 

 spirit, and glycerine to 20 of water) ; 24 hours are allowed to elapse 

 between the two injections. It is a good thing to introduce a little 

 dilute injection fii'st. 



Staining with Saflranin.t — According to W. Pfitzner, staining 

 with saffranin is most successful with chromic acid preparations which 

 have been entirely freed from the acid, less so with substances 

 hardened in picric acid ; the only tissues suited to it are those which 

 very readily take up colom-, and these must be cut extremely thin. 

 The sections are transferred to the staining fluid (1 part saffranin, 100 

 absolute alcohol, 200 distilled water) from distilled water, are again 

 placed in distilled water after a few seconds, and then into absolute 

 alcohol, from which they are removed at the right moment (i. e. when 

 the nuclei are properly stained) to dammar varnish. The advantage 

 of staining with saffranin is that it affects the nuclei exclusively. Dr. 

 M. Flesch J remarks that the advantage claimed by Pfitzner for 

 saffi'anin has been shown by Hermann to be shared with it by other 

 aniline dyes when applied in the same manner. 



Staining with Silver Nitrate. — Staining with nitrate of silver is 

 very difficult to effect in the case of marine organisms, owing to the 

 abundance in which chlorides occur in them. E. Hertwig § meets this 

 difficulty by washing the animals (after hardening in osmic acid) with 

 distilled water until the water used for washing gives but a very 

 slight precipitate with solution of silver nitrate, and then allowing a 

 1 per cent, solution of the nitrate to act for 6 minutes. 



* Arch. f. Anat. u. Entwick., 1880, pp. 232-4. 



t Morph. Jahrbuch, vi. (1880) p. 469. Cf. Zool. Jahresber. Neapel for 1880, 

 i. p. 43. 



X Ibid., pp. 43-4. 



§ Jen. Zeitschr., xiv. (1880) p. 324. 



T 2 



