Journal of Applied Microscopy. 



361 



medium is to be made, one part of a one or two per cent, glucose bouillon is 

 added to every three parts of blood-serum before tubing. 



After filling all the tubes which it is desired to prepare, the remaining portion 

 of the liquid serum may be kept for future use by pouring it into bottles and 

 adding a sufficient amount of chloroform to form a layer of '2 mm. to 3 mm. on the 

 bottom. The bottle is then closed with a tightly fitting cork Qio^ with a cotton 

 plug), thoroughly shaken, labeled, and set aside. This will preserve the serum 



Fig. ]. 



indefinitely, and it is available for use at any future time by vaporizing the 

 chloroform. 



To return to our tubes : after filling, the next step is the one to which I 

 desire to direct special attention, as careful observance of this point obviates all 

 difficulty connected with solidifying the serum without bubbling. A number of 

 corks of the best qualitv. and one or two sizes larger tJian will easily go ifito the 

 mouth of the tube, are put into a wire basket and steamed in the Arnold sterilizer 

 for at least twenty minutes. When taken out they will be both sterilized and so 

 softened that they can readily be forced into the tubes for some distance. The 

 cotton plug of each test-tube is then burned ofT to a level with the top of the 

 tube and the cork shoved well in, care being taken to avoid contamination of the 

 cotton and cork during this procedure. Then, by means of a fairly stout piece 

 of twine, each cork is tightly tied into its tube, using the knot commonly 

 employed by druggists for this purpose (Fig. 1). A lipped test-tube (the usual 

 kind) must be employed. The tubes used by the New York and other health 

 departments will not answer. 



After tying in all the corks, the tubes are placed on the proper slant in a 

 receptacle which can easily be made from a cigar box and a piece of wire gauze 

 such as is used for fly screens. 

 No description of this apparatus is 

 necessary, as its construction is 

 well shown in Fig. 2. 



Having filled the box, preferably 

 with a single layer of tubes, a wire 

 basket, such as is found in every 

 bacteriologic laboratory, is placed 



Fig. 



upright in the Arnold sterilizer, and upon this is laid another, flat. On the 

 latter is placed the box of tubes. This should bring the tubes about to the level 

 of the top of the sterilizer, where they can be easily observed, and where, in the 

 method used, the temperature falls just short of 100° C. A towel, of not too 

 close weave, is then thrown over the sterilizer. This should be the only cover, 

 both inner lid and outer jacket of the sterilizer being dispensed with (Fig. 3). The 



