94 



THE AMEKICAN MONTHLY 



[May, 



niacal carmine for similar purposes, 

 but is more convenient and has the ad- 

 vantage that it may be applied in defi- 

 nite quantities. Like Hoyer's, it is 

 well adapted for double staining and 

 for picro carmine, and is much to be 

 preferred to the commercial article 

 called by Hoyer's name. 



I add here a few carmine prepara- 

 tions whose authors I can give, but 

 not date and place of publication. 

 Some of them are among those best 

 known : — 



32. Frey. Das Mikroskop und die 



Mikroskopische Technik. 7 

 Aufl., Leipzig, 1S81. (Lithe 

 3 Aufl., 1868, not given.) 

 Dissolves carmine in acetic acid, 

 adds water, and filters. 



33. Perls. Nach mlindlicherMitthei- 



lung an Frey. Li dessen, das 

 Mikroskop und die Mikrosko- 

 pische Technik. 7Aufl.,iSSi. 

 Perls finds that the carmine now in 

 market is sufficiently soluble in water 

 to make a stain. (This does not ap- 

 pear true of all kinds ; my best is al- 

 most wholly insoluble.) He recom- 

 mends the following method : Car- 

 mine is slowly boiled for an hour in 

 water, then filtered. The filtrate is 

 at first cloudy. It is to be repeatedly 

 passed through the same filter till of 

 a clear red. Perls thinks it stains 

 chromic acid preparations better than 

 ammoniacal carmine. 



(I do not consider the above to com- 

 pare favorably with ammoniacal car- 

 mine or sodium carminate, because it 

 does not give clear stainings.) 



34. Rollet. 



Recommends carmine in water. 

 Boils ordinary carmine with dilute 

 sulphuric acid a precipitate of fer- 

 mentible sugar, and a dark red mass 

 Cj ^ Hj 2 O^ is obtained, slightly sol- 

 uble in water and alcohol. It pos- 

 sesses no advantages over carmine 

 (carminic acid). 



35. Ranvier. 



Recommends clearing difluse stain- 

 ings in formic acid instead of acetic 

 or muriatic. (Glycerin 100 to i of 

 formic acid). 



In this connection I must protest 

 against the numerous objections to 

 the use of ammoniacal carmine. I 

 have kept concentrated solutions a 

 year without mould, and have some 

 that is eight years old. It is true it 

 was made from the best carmine of 

 the old make. The early directions 

 succeed well, even with chromic acid 

 preparations ; want of success is usu- 

 ally due to bad manipulation or a bad 

 quality of carmine. A slight addi- 

 tion of ammoniacal salts (possibly 

 others also) improves its action very 

 much, 'and may be necessary for 

 some purposes. Old ammoniacal 

 carmine always contains ammonium 

 carbonate or bicarbonate through ab- 

 sorption of carbon dioxide from the 

 air. 



Although it may seem from this 

 collection that a sufficient number of 

 processes for staining with carmine 

 already exist, and perhaps some we 

 could well dispense with, yet I will 

 add one I employed long ago for 

 staining the great nerves. It is es- 

 pecially to be recommended when 

 the material has lain too long in alco- 

 hol after hardening by chromic acid, 

 or after too much chromic acid, the 

 carmine does not stain deeply enough. 

 I lay the sections for 24 hours in a 

 1% watery solution of uranium nitrate, 

 sulphate, or chloride, wash them 

 well, and treat them 10 to 24 hours 

 with dilute ammoniacal carmine. 

 The preparation, colored by the ura- 

 nium salt slighth' yellow or green, 

 takes a dark purple ; the nuclei are 

 better shown than with carmine 

 alone ; the nerve cells and their pro- 

 longations are extremely clear. This 

 method may be applied to other or- 

 gans, but does not for them have 

 especial advantages. A purple stain- 

 ingfluid maybe made by adding some 

 of the uranium salts to a dilute am- 

 moniacal carmine solution, and fil- 

 tering after some hours. This dyes 

 nerves very clearly, but I prefer the first 

 method. Carmine is often used for 

 double staining, which see. /^ / 



[ To be continucii.'\ f / ^ ^ 



