and Laboratory Methods. 1713 



A second method of staining makes it possible to mount the preparation in 

 balsam. It is as follows : A 5 per cent, or 10 per cent, solution of gentian 

 violet or fuchsin is used. This is placed on the dry and fixed cover-glass prep- 

 aration and gently heated until steam rises. The dye is washed off with a 20 

 per cent, solution of copper sulphate (CuSo^ crystals) and the preparation is dried 

 and mounted in balsam. By these methods most streptococci have been shown to 

 have capsules. h. w. c. 



Hill, Hibbert W., M. D. "Hanging Block" The writer cuts a cube of nutrient agar 

 Preparation for Microscopic Observation of from a Petri-dish full of solidified jelly. 

 Developing Bacteria. Boston Board of -phe organism to be examined, as an 

 Health, Bact. Lab. , . ° . ^ ^ ' , 



emulsion m water from a solid cul- 

 ture, or as a drop of broth from a liquid culture, is spread upon the upper surface 

 of the agar, as in making an ordinary smear preparation on glass. After drying 

 the cube at 37° C. for 10 minutes, a clean coverslip is applied to the inoculated 

 surface and sealed in place by running a little melted agar round the edges of 

 this surface. The coverslip is then placed over the opening in the moist cham- 

 ber, the agar block lowermost, and the microscope focused upon the bacteria. 

 For organisms growing best at 37° C. some form of warm chamber is necessary. 

 The writer describes two such warm stages, devised by himself, and a very simple 

 method of securing a circulation of warm water through them. h. w. c. 



Gorsline, C. S. An Improved Method of The useof collodion sacs in bacteriologi- 

 Making Collodion Sacs. University of ^^^ investigations has come to be quite 

 Michigan. . ° r^., 7 , 



common in recent years. The methods 



of producing these sacs have been somewhat difficult. Gorsline has added one 

 point of simplification to the methods that have previously been used, which 

 renders the production of such sacs a very much simpler operation than it has 

 been hitherto. Indeed, it is now, by the new method, an extremely simple matter 

 to produce collodion sacs of practically any desired size. The method which 

 Gorsline has devised and described is as follows : 



A long tube is prepared, closed at one end, except for a minute perforation 

 at the bottom, from 2 to 4 millimeters in diameter. A wide mouthed bottle, 

 holding 6 to 8 ounces, is filled about one-third full of colorless collodion of the com- 

 mon strength. The first step is to touch the end of the tube to the surface of the 

 collodion, thereby obtaining a film of collodion over the small opening, but allow- 

 ing none to enter the inside of the tube. This is allowed to dry for a few moments 

 and harden. The bottle containing the collodion is then inclined as much as 

 possible without spilling, the tube inserted into the collodion and slowly rotated, 

 allowing the lower fourth of the tube to be immersed in the collodion. 



The tube is withdrawn from time to time to allow a partial drying to take 

 place ; the operation being repeated until the desired thickness is reached. Two 

 or three coats thus obtained are commonly sufficient. As soon as the collodion 

 has set, the tube may be immersed in water at about 25°, to hasten the drying 

 of the sac. When this is ended, distilled water is put into the open end of the 

 tube, and by applying the mouth, the water is forced through the perforation in 

 the tube at the bottom, carrying the collodion ahead of it. By blowing into the 

 tube the water is caused to creep in between the sac and the tube, gradually 

 separating the collodion sac from the glass, the process being aided and made to 

 progress evenly on all sides by twisting and shifting back and forth the free end 

 of the sac. When the water has risen to the top of the sac, the latter slips off 

 from the glass easily into the hand. The water by its pressure not only releases 

 the sacs, but tests it for weak places and for perforations. 



Collodion tubes may be thus made from one-sixteenth of an inch to two inches 

 in diameter, and prove to be extremely useful, not only for bacteriological ex- 

 experiments, but for dialyses. The rapidity with which the process of dialysis 

 goes on through these sacs is very great. h. w. c. 



