2052 Journal of Applied Microscopy 



The first trials of Chloretone were so successful that a series of careful studies 

 extending through several weeks were undertaken to determine the range of its 

 usefulness and the formulae for its use on a large number of species of animals 

 from the Protozoa to Amphibians, and in a minor surgical operation on a valu- 

 able dog. The results exceeded all expectations as to its value in the projec- 

 tion of live animals, and also led to its introduction into regular laboratory work. 

 The methods of use were demonstrated to the teachers of biology in the Chicago 

 high schools in the fall of the same year, and were included in a course of 

 instruction in Biological Projection in the University of Chicago in the summer 

 of 1901. On the basis of the experience of the writer and the satisfactory 

 results reported by other teachers who have used it, the Chloretone method of 

 anesthesia is offered as a useful addition to laboratory methods in zoology, as 

 well as an indispensable adjunct in the projection of live animals for the pur- 

 pose of careful study or while being photographed. 



Chlorotone, having the formula C4H.OCI3, is a white crystalline compound 

 with an odor and taste resembling camphor. It is usually obtained in bulk in 

 the form of fine crystals for laboratory use, but is also sold in sugar-coated tab- 

 lets and in capsules, which is its most convenient mode of administration to some 

 of the lower vertebrates. The crystals are added to clear water, not distilled, 

 at ordinary room temperature, and in the proportion of one part Chloretone to 

 ninety-nine of water by weight or Chlorotone crystals one gram, water !)9 c.c. A 

 solution of approximately the same strength may be prepared by adding enough 

 of the crystals to water to form a saturated solution. The crystals dissolve 

 slowly and two days, or more, are required for the solution to reach its maxi- 

 mum strength of one per cent. The solution should always be made up and 

 kept in a tightly stoppered bottle on account of the volatility of the Chloretone, 

 and the crystals need the same care. The one per cent, stock solution remains 

 unchanged for months. In use it is diluted with tap, well, or river water, to the 

 degree of strength required by the animals which are to be treated. With a few 

 species, the undiluted solution, the tablets, or capsules are used. At first thought 

 the expense seems to be great, as Chloretone crystals cost about one dollar per 

 ounce ; but this amount will make about three quarts of one per cent, stock 

 solution, four and a half gallons of the strength most commonly used, and the 

 average cost per student per year will be less than five cents. 



The usual mode of administering Chloretone to aquatic animals is by 

 immersing them in a solution of suitable strength. The tray or other container 

 in which the animals are placed should be chosen with a view to having them 

 completely covered, when a relatively small amount of solution is added. Place 

 the animals, one or enough for an entire class, in a tray, and pour on them a 

 sufficient quantity of solution of the proper strength to cover them, or, if more 

 convenient, place the animals in a measured quantity of water and add enough 

 one per cent, stock solution to bring it to the right degree of dilution. The 

 action of the Chloretone is such that great accuracy is not necessary in ordinary 

 work. If the animals are distributed to the members of a class for examination 

 and are found to be either too slightly or too profoundly anesthetised, one or 

 more drops of stock solution may be added or the solution diluted with water. 



