ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 703 



The use' of metallic instruments is to be avoided, beeause, being 

 attacked by tbe bichloride of mercury, tbey give rise to cloudy pre- 

 cipitates, which render the prepared objects thick. Sections should 

 be cut before plunging them in the solution, and when it is necessary 

 to tease out the elements of a tissue it should be done with porcupine 

 quills or pointed goose-quills. 



If it is wished to preserve red blood-corpuscles, the blood must be 

 diluted with at least 50 to 100 times its volume of solution II. (or 

 No. III., see above) ; this is decanted after the lapse of 24 hours, and 

 changed in the same way three or four times. White blood-corpuscles 

 may be isolated by destroying the red ones ; this end is attained by 

 the use of solution IV., by means of the acetic acid contained in it. 

 It must be applied for 48 hours in the proportion of from 50 to 100 

 times the volume of the blood, and must, as in the former case, be 

 changed three or four times. If transferred to solution II., the 

 leucocytes gradually regain their original form. Spermatic fluid is 

 preserved in solution II. The liquid must first be stirred round 

 with a glass rod to prevent the elements adhering. 



Epithelia are examined in the same solution after the parts which 

 support them have remained some days in the solution, spread out, if 

 necessary, on sheets of guttapercha with cactus thorns. 



Blood-vessels may be beautifully injected naturally by putting 

 the tissues which contain them into solution II. or III. for a con- 

 siderable time (fostus eyes intended to show the vessels of the 

 pupil lar membrane should be treated thus for 20 days). Nerve-fibres 

 may be studied advantageously in the cranial and intra-ocular nerves 

 with their comparatively thin medullary sheaths. Muscular fibres 

 are best examined in the muscles of Petromyzon after a treatment of 

 several days with solution IL 



If it is desired to collect Infusoria or other very small organisms, 

 animal or vegetable, particularly when they are in movement and scat- 

 tered through a large quantity of water, a tolerably large glass vessel 

 (in order to collect a sufficient quantity) should be filled with the 

 water, and a little of the solution No. II. added. All the Infusoria 

 being killed by the bichloride of mercury, they fall slowly (in three 

 or four days) to the bottom of the vessel, the more slowly as they are 

 smaller. The greater part of the liquid is then to be decanted by a 

 siphon and replaced by some of the solution, which should be changed 

 three or four times. The Infusoria can then be preserved in a bottle 

 or mounted. 



Preparing Sections of Axis- cylinder. — For extensive lengths 

 of axis-cylinder G. Bufelius * proceeds as follows : — Fragments of 

 nerves of the dog or rabbit are laid for 24 hours in Muller's fluid. 

 They are then transferred to an aqueous solution of corrosive sub- 

 limate ( • 5 per cent.) in which they remain several days, the liquid 

 being constantly changed, until the solution undergoes no further 

 alteration. The tissue is then teased and treated with dilute picrc- 



* ■ Lo Sperimentale,' 18S0, Nov. Cf. Jabresber. Virchow and Hirsch for 1880, 

 p. 22. 



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