100 THE AMERICAN MONTHLY [April, 



in packages of 500 sheets, 10 x 7 Inches, at $1.00, and 100 sheets, 

 10 X 7 inches, at 25c. 



It is for sale by nearly all dealers in microscopes and materials. 

 G. S. Woolman, 116 Fulton st.. New York, is the one who has 

 introduced these cheap packages. 



Glue for Labels. — (i ) Dissolve at a moderate heat 2 parts of 

 white gelatine and i of rock candy in 3 of water. 



Or (2) dissolve at moderate heat 9 oz. glue, 4^^ oz. rock cand}', 

 I J oz. gum arable in i part of rain or of distilled water. 



Use of Hydroxylamine. — In preserving specimens for micro- 

 scopic use, the following-named difHculty is frequently encoun- 

 tered. With death comes a muscular contraction of certain organs 

 to such an extent as to obscure the points we desire to observe. 

 In mounting various infusoria there is difficulty in fixing them in 

 the best attitude. The preservative reagents cause rotifers and all 

 kinds of molluscs to shrink. 



The old method of procedure was to try to kill the specimen in- 

 stantly catching it in a distended condition. But Dr. Bruno 

 Hofer has proposed to paralyze the contractile organs and to 

 then hx the paralyzed animal. After using with more or less 

 satisfaction cocaine, antipyrine, chloral, and other alkaloids, he 

 settled upon hydroxylamine as by far the most efficient. With 

 it paralysis is secured before the protoplasm in the cells has 

 swollen perceptibly. 



The following directions are given for using hydroxylamine : 



One per cent, of the crystals of the commercial hydrochlorate, 

 which are usually impure, is dissolved in fresh water, and enough 

 carbonate of soda added to render the solution neutral. This solu- 

 tion may be kept on hand in large quantities for use at any time. 

 Distilled water must not be used in preparing it, but in the case 

 of marine forms salt water must necessarily take the place of fresh. 

 It is not advisable to eliminate the hydroxylamine from the hydro- 

 chlorate solution by adding an excess of carbonate of soda, as the 

 li(|uid then obtained would over-excite the animal. After the ani- 

 mals have been paralyzed in the neutral hydrochlorate solution 

 they are immediately covered with the fixing medium and thereby 

 killed. 



The number of fixing reagents that may be used is, of course, 

 limited. For, hydroxylamine being a powerful reducing medium, 

 all easily reducible agents, such as osmic acid, corrosive sublimate, 

 chloride of gold, of platinum, etc., cannot be directly applied. 

 The hydroxylamine must first be worked out with water. Alco- 

 hol, acetic, and picric acids, and mixtures of these two acids may 

 be directly applied, and with these a good histological slide may 

 always be obtained. 



The strength of the solution depends, of course, on the nature 

 of the animal to be mounted. 



