METHODS FOB INVEKTEBIUTES. 463 



Kaisee {Biblioth. Zool., H. vii, 1 Halfte, 1891, p. 3) found 

 that a saturated aqueous solution of cyanide of mercuiyj 

 warmed to 45° to 50° C, and allowed to act for from fifteen 

 to sixty minutes, and then washed out with 70 per cent, 

 alcohol, was the best of all fixing media. 



888. Nematodes — The impermeable cuticle is a great obstacle 

 to preparation. According to Looss [Zool. Anz., 1885, p. 

 318) this difficulty may be overcome in the manner described 

 in § 553. 



For fixing, most recent authors recommend sublimate 

 solutions ; chromic solutions seem to have a tendency to 

 make the worms brittle. 



But, according to Zde Steassen {Zeit. wiss. Zool., liv, 

 p. 655), Bradynema rigidum ought to be fixed for at least 

 twelve hours in mixture of Flemming. 



AuGSTEiN {Arch. Naturg., \x, 1894, p. 255) takes for 

 Sirougyius filaria Mayer's picro-nitric acid. 



Vejdovsky [Zeit. iviss. Zool., Ivii, 1894, p. 645) advises for 

 Gordius 0"5 per cent, chromic acid (twenty-four hours). 



Lo Bianco employs for marine forms concentrated subli- 

 mate or picro-sulphuric acid. 



Looss {Zool. Anz., xxiv, 1901, p. 309) prefers hot (80° to 

 90° C.) alcohol of 70 per cent. 



Glaue {Zeit. iviss. Zool., xcv, 1910, p. 554) kills Ascaris 

 in a hot mixture of 100 parts of saturated sublimate, 100 of 

 alcohol, and 1 of acetic acid. 



Staining is frequently difficult, and sometimes alcoholic 

 carmine, § 234a, is the only thing that will give fair results. 



Beatjn (see Journ. Roy. Mic. Soc, 1885, p. 897) recommends that 

 small unstained Nematodes be mounted in a mixtui-e of 20 pai-ts gelatin, 

 100 parts glycerin, 120 parts water, and 2 parts carbolic acid, which is 

 melted at the moment of using. Canada balsam, curiously enough is 

 said to sometimes make Nematodes opaque. 



Demonstration of living Trichinx. — Barnes (Amer. Mon. mile. Journ., 

 xiv, 1893, p. 104) digests triohinised muscle (of the size of a pea) in a 

 mixture of 3 gr. of pepsin, 2 di-. of water, and 2 minims of hydrochloric 

 acid, kept at body temperature for about tlu-ee hours. The flesh and 

 cysts being dissolved, the fluid is poured into a conical glass, and 

 allowed to settle ; the trichinae are drawn ofE from the bottom with a 

 pipette, got on to a slide with water and examined on a hot stage. 



Gkaham (Arch. mile. Anat., 1, 1897, p. 216) isolates Trichinas by 



