and Laboratory Methods. 2179 



The Technique of Biological Projection and Anesthesia of 



Animals. 



COPVRIGHTED. 



XI. THE ANESTHESIA OF ANIMALS.— Continued. 



Vermes : Leeches. — For studying the anatomy of leeches in the live state 

 small specimens showing the greatest degree of transparency should be selected 

 and placed in water, five parts, with one per cent, chloretone solution, two parts. 

 The animals soon become motionless and lose their power of adhesion to the 

 dish, and should then be mounted in a compressor, with enough of the anesthe- 

 tizing solution to surround them. A gravity compressor, as illustrated and de- 

 scribed in the directions for the study of earthworms, is useful for leeches. 

 Specimens bearing ova or young attached to the ventral surface are best studied 

 in a watch-glass, with just enough solution to cover them. Young leeches, when 

 treated as above described, soon release their hold on the adult and lie quietly 

 in the watch-glass. If sufficient water is soon added to dilute the chloretone 

 solution to one in five, or weaker, the little leeches revive, find their mother, 

 and reattach themselves. In species having a protrusible proboscis, this organ 

 is often freely extended under the influence of chloretone, and they may be 

 killed in this condition by the addition of a suitable killing agent after com- 

 plete anesthesia has been induced. 



Rotifers. — Chloretone is a valuable adjunct to the compound microscope in 

 the study of these interesting and, in many species, active animals. To study 

 the action of their cilia, the mastax, and anatomy, mount either free-swimming 

 or attached species in a hollow-ground slide, in a watch-glass or on a plane slide, 

 and add one per cent, chloretone solution, drop by drop, while observations are 

 being made. Ciliary action continues after complete somatic anesthesia has been 

 induced and, by grading the amount of chloretone properly, any desired rate of 

 ciliary activity between normal and complete quiet may be had. 



Arthropoda. — The value of chloretone in studies of animals of this type is at 

 once evident, when we consider that reduced rates of motion of their append- 

 ages, and the possibility of placing the live animals in the best position for study 

 with hand lens, and dissecting or compound microscopes, are conditions of suc- 

 cess not so easily attained by any other method. Moreover, the action of the 

 anesthetic is such that the movements of the mouth parts are unusually well dis- 

 played in many species. The method is limited, as yet, in its application to 

 aquatic species and to others which live in moist places and may be immersed 

 in chloretone solution without drowning. 



Crayjish. — Adult crayfish should be placed in full strength, /. e., one per 

 cent., chloretone solution, sufficient to cover them, and allowed to remain for 

 twenty minutes, or until anesthesia is sufficiently complete for the desired 

 studies. Young crayfish, just out of the egg, require a solution of water, five 

 parts, one per cent, chloretone solution, one part. The most interesting and 

 instructive stage for the study of crayfish is during the three or four days fol- 



