Apbil 30, 1915] 



SCIENCE 



663 



Tvater until the filtrate no longer gives a test for 

 sulphuric acid. As the volume of the suspension 

 finally drains down to about 200 c.c. any deposit 

 of cellulose on the filter may be removed vrith a 

 camel 's-hair brush. A hole is then punched in the 

 bottom of the filter and the whole precipitate 

 washed out and made up to 500 c.c, when it may 

 be added to 500 e.e. of 1-per-cent. agar containing 

 the nutrient salts. Cellulose-destroying bacteria 

 "were plated on a medium containing cellulose pre- 

 cipitated by this method and on one containing 

 cellulose from Schweitzer solution. The destruc- 

 tion of the cellulose was about the same in both 

 media. 



New Technique for Studying Halophytic Organ- 

 isms: K. F. Kelleeman and N. E. Smith. 



1. For staining flagella from salt media the 

 bacteria are placed in a salt water suspension, 

 killed by addition of 10 per cent, formalin, then 

 placed in collodion dialyzing tubes and the soluble 

 salts removed by dialysis. The bacteria are thrown, 

 down by eentrifnging, and the residue spread on 

 clean slides and stained by any method desired. 



2. For isolating bacteria injured by heating to 

 42° C, use silica jelly. This can not be mixed 

 with beef broth or peptone. When these nutrients 

 are desired, pour sterile Petri plates of beef agar 

 or peptone agar, allow them to harden for twenty- 

 four hours, then for the isolating medium use 

 synthetic salt solution and silicic acid solution, and 

 pour this rapidly over the sterile beef or peptone 

 agar plates and allow to remain perfectly quiet. 

 The silica jelly forms a layer over the agar layer 

 and the nutrients mix by diffusion. 



3. Use collodion sacs to maintain constant sup- 

 ply of slightly soluble salts in clear solutions in 

 bacterial culture flasks. 



The Eelaiive Merits of the Bubbling Method of 

 Enumerating Air Bacteria: John J. Wenner. 

 The writer is making a study of the modified 

 Petri sand filter and the Eettger aeroscope bub- 

 bling filter for the purpose of determining their 

 relative degree of efficiency, simplicity and prac- 

 tical value. The sand filter was, at first, set up as 

 described in a previous paper by "Weinzirl and 

 Thomas ('12). As this apparatus was very cum- 

 bersome, it was soon modified by discarding one 

 stopper entirely, holding the sand in the tube by 

 means of a tight wire gauze, and attaching the 

 aspirating tube directly to the main filtering tube. 

 The great weakness of the sand filter is in the 

 transference of the organisms caught in the sand, 

 to the plate, so as to be easily and accurately 

 counted. This was done in three ways: (1) The 



sand was distributed among several sterile plates 

 and gelatin added. (2) The sand was transferred 

 to a small sterile flask holding 10 c.c. of salt solu- 

 tion and an aliquot part plated. (3) The sand 

 was transferred to a sterile test-tube holding 5 c.c. 

 of salt solution, thoroughly washed, and the liquid 

 plated with an equal amount of strong gelatin. 

 This last method appears to be the most practical. 



The Eettger aeroscope was used as originally de- 

 scribed by Eettger ('10). A second plate, from 

 washing the aeroscope and test-tube, should, in all 

 cases, be poured. 



The two filters were run simultaneously and con- 

 secutively under similar conditions. Air was taken 

 in a dusty attic room and from a specially pre- 

 pared box. 



Both methods are equally simple and both filter 

 with a high degree of accuracy. In plate pouring 

 the aeroscope is simpler and contamination is not 

 so easy. Besides the bubbling method is visible 

 and audible, which may at times be very desirable. 

 The writer's work has not been completed, but 

 from his results thus far obtained the bubbling 

 method gives him an excess in the number of col- 

 onies, over the sand filter. As technique is very 

 delicate, a large number of tests have to be made 

 for the results to be of any value. 



One of the great drawbacks in the practical use 

 of the air filter is the inconvenience of the as- 

 pirator. "We need an aspirator that is easily trans- 

 ferred from place to place, one that is simple and 

 yet will give a fair degree of accuracy, as well as 

 a uniform and continuous rate of flow. For this 

 purpose the writer has been experimenting by 

 placing two movable tanks in a wooden box. The 

 tanks are connected with a rubber tube while 

 another tube from each tank extends to the out- 

 side. The filter is attached to the proper tube and 

 the water passed from one tank to the other. 



Suggestions for Partial Anaerobic Cultures: Ward 



GiLTNEE. 



Anaerobiosis and aerobiosis are relative terms. 

 The oxygen requirements and tolerance of micro- 

 organisms present a gradation from practically an 

 absence of oxygen pressure to many times atmos- 

 pheric pressure. The lowering of oxygen tension 

 by biological means, Nowak's B. subtilis cultures, 

 was introduced in connection with the growth of 

 Bact. aiortus, an organism requiring a slightly 

 lower oxygen pressure than atmospheric. In this 

 method the oxygen-consuming culture and Ba-ct. 

 abortus are usually grown in vitro separately, the 

 two cultures being placed in a Novy or similar 

 sealed jar. A simpler method is desirable. Ee- 



