and Laboratory Methods. ^^^1 



The Technique of Biological Projection and Anesthesia of 



Animals. 



Copyrighted. 



VIII. THE ANESTHESIA OF ANIMALS. 



Before entering into the details of the methods of mounting various types of 

 live animals and plants and the forms of cells best adapted to hold them on the 

 projection microscope while they are being used in the production of living 

 charts, it is desirable that the methods of producing anesthesia should be 

 explained. The present tendency in biological teaching to emphasize the study 

 of live organisms in their natural habitat or engaged in their normal activities 

 in the more or less artificial environment of the laboratory, is worthy of the 

 largest recognition and universal adoption, but the practical impossibility of 

 controlling active animals on the laboratory table, or stage of the microscope, 

 has been a serious obstacle to the attainment of a desirable degree of definite- 

 ness in these lines of work. By the use of a suitable anesthetic, nearly all the 

 animals studied in elementary courses in zoology and a large number of other 

 species may be very easily put to sleep and in this state are peculiarly adapted 

 to careful study under the hand lens, compound microscope, and projection 

 microscope. The degree of quiet may be varied from true hypnosis, or the con- 

 dition of sleep, in which the voluntary muscles only are passive and all other 

 parts are normally active, through different degrees of partial to complete anes- 

 thesia, and to the death of the animal, if this is desired. The hypnotic condi- 

 tion is most desirable in ordinary studies, since it is more quickly induced, is 

 seldom, if ever, fatal, and while it lasts, if no pain is inflicted on the animal, the 

 voluntary muscles remain passive and limp, affording the best conditions for the 

 study of normal structures, functions, and such vital phenomena as the pulsation 

 of the heart and the actual movement of its valves. By carefully grading the 

 strength of the anesthetic, animals may be kept for extended periods of time on 

 the border line between normal activity and sleep, and at the conclusion of the 

 experiments revived and used again and again during the same or succeeding 

 days. The methods are so simple and the anesthetising agent so safe for stu- 

 dents to use that they readily learn how to do the work and accomplish satisfac- 

 tory results. It may be remarked, in passing, that the lively interest awakened 

 in the students as they use these methods is a pedagogic factor of no small 

 importance. 



It is not our purpose to enter into a discussion of the relative values of the 

 different chemical compounds which have been used with varying success in the 

 anesthesia of the lower animals, but to proceed, at once, to the consideration of 

 the one believed to be the best and having the widest range of usefulness. A 

 few years ago a new hypnotic, called Chloretone, was brought to the attention 

 of the medical fraternity by its manufacturers, Parke, Davis & Co., of Detroit, 

 Mich. In the spring of 1900 a description of the chemical and of its use on 

 the human subject awakened the hope that it would give better results than 

 other agents in the control of animal motion during projection experiments. 



