SEIUAL SECTION MOUNTING. 121 



moisture from the breath should condense on it evenly all 

 over, and disappear evenly. Secondly, streaks of water 

 drawn on it with a brush should not run. To obtain a slide 

 that will fulfil these conditions, clean it well in the usual 

 way, place a drop of water on it and rub it in thoroughly 

 with a damp cloth and try the tests. If this does not 

 suffice, take a turn of a corner of the cloth round a finger 

 and rub it with a piece of chalk, then damp the cloth and 

 rub the slide with it, finishing up with a clean part of the 

 cloth and clean water (Djs Groot, loc. cit. supra). If after 

 performing this operation twice the slide still refuses to take 

 the water thoroughly, it should be rejected as incorrigible ; 

 for there are apparently some sorts of glass that can never 

 be got to wet properly. Mayer finds cai-bonate of magnesia 

 or soda useful. 



GuDEENATSCH [Zeit. wisn. Mihr., xxiv, 1908, p. 358) washes 

 the slide well with potash soap, and arranges the sections 

 on it whilst still wet. Helly [ibid., 1906, p. 330) passes it 

 two or three times over the flame of a Bunsen burner. 



Tap water seems preferable to distilled water ; it seems to spread 

 better and give a stronger adhesion. Ntjsbatjm adds a trace of gum 

 arabic (one or two drops of mucilage to a glass of water) ; Apathy 

 {Microtechnik, p. 126) adds 1 per cent, of Mayer's albumen (§ 187) ; and 

 Hbnnegtjt (Lefons sur la Cellule, 1896, p. 62) takes a 1 : 5000 solution 

 of gelatin, with a trace of bichromate of potash, added just before 

 using, and dries the slides exposed to light. Similarly, Btjechaedt 

 {Jena Zeit., xxxiv, 1900, p. 719). 



Some workers have used alcohol (50 per cent, or 70 per cent.) instead 

 of water ; but this I believe to be now generally abandoned. 



This is the most elegant method of any, as there is 

 nothing on the slide except the sections tliat can stain, or 

 appear as dirt in the mount. Tissues do not suffer from 

 the drying, provided the material has been properly 

 imbedded. Sections stick so fast by this method that they 

 will stand watery or other fluids for weeks, so long as they 

 are not alkaline. When successfully performed it is quite 

 safe, provided that the sections are of a suitable nature. 

 They must be such as to afford a sufficient continuous 

 surface, everywhere in contact with the slide. Sections of 

 parenchymatous organs stick well ; sections of thin-walled 

 tubular organs stick badly. Sections of chitinous organs 



