700 



SCIENCE 



[N. S. Vol. XLII. No. 1089 



the large relevant literature of the subject, 

 dealing with ideas which richly deserve a 

 more leisurely and scholarly development. It 

 is to be hoped that Dr. Crile may in the near 

 future find time for such a treatment. 



James R. Angell 

 The Univeksity of Chicago 



SPECIAL ARTICLES 

 A STERILE SIPHON TIP PROTECTOR 



The tip of a siphon supplying sterile water, 

 physiological saline solution, or diluent (0.4 

 per cent, tricresol in 0.85 per cent. NaCl so- 

 lution) for various bacteriological procedures 

 must be protected from contamination by dust, 

 flies or other unsterile objects. This is accom- 

 plished fairly successfully with a bell-shaped 

 cap such as can be made by cutting the bulb 

 of a 50 c.c. volumetric pipette in the middle, 

 leaving attached to each bell a tube 5-7 cm. 

 long for union with the siphon tube, and 

 drawing into this tube by means of a suitably 

 sized rubber hose, another glass tube of such 

 size that when the rubber hose is released its 

 elasticity binds the two together. The covered 

 end of the smaller tube is then adjusted even 

 with that of the bell tube and the rubber hose 

 snipped off, or in fact used to connect to the 

 siphon of the bottle. 



But such a device, while giving a fair pro- 

 tection during use, does not prevent the lodg- 

 ment of upwardly floating particles of lint 

 upon the drop of liquid at the point. It is this 

 protection which the following addition ac- 

 complishes. 



A test tube about 2.5 cm. X 15 cm. may 

 usually be found to fit outside or inside the 

 bell, as above prepared. The lip is removed 

 and upon the tube is placed a thin rubber 

 finger cot or a finger of a rubber glove from 

 which the closed end has been cut so that the 

 portion which is left may be rolled upon the 

 bell from the tube thus holding the two to- 

 gether and preventing lodgment of contamina- 

 ting dust when the siphon is out of use. Dur- 

 ing use the protector may itself be protected 

 by fastening it to another test tube. How- 

 ever, this is scarcely necessary, and I have 

 ordinarily taken no particular precautions to 



sterilize or prevent contamination of the pro- 

 tector since it touches the bell only and not 

 the siphon tip itself. Yet in certain permis- 

 sible cases a few drops of formaldehyde in the 

 protector have added a further element of 

 safety. 



One of the special purposes to which I have 

 successfully adapted such a device is the fre- 

 quent examination of bacterial broth cultures 

 being studied for progressive metabolic and 

 morphological changes. For example, some of 

 the fluid from a liquid preparation of B. 



u 



diphtherioe was withdrawn every four days for 

 a period of three weeks, microscopic and cul- 

 tural examinations made at each withdrawal 

 confirming the continued purity of the con- 

 tained culture. 



Fig. 1 shows a diagrammatic cross section of 

 the apparatus set up (.A) and taken apart (B), 

 for use of the siphon. 



Ivan C. Hall 



The Cutter Biological Laboratoeies, 

 Bekei:ley, Calif. 



