22 



GENERAL TECHNIC 



4-\ 



7- 



4 _ GRADUATED PIPETS. 



accurate measurement of small amounts of 

 fluid. The entire length of these pipets is 

 equal to the ordinary 1 c.c. pipet which 

 renders the subdivisions far apart and quite 

 easy to read (Fig. 4) . These pipets are made 

 by competent dealers upon special request. 



2. These pipets should be perfectly 

 clean and clear, sterilized, and have sharp, 

 easily read markings. Pipets with broken 

 tips are difficult to handle, and if calibrated 

 to the tip, are inaccurate. 



3. The worker should practise methods 

 of making accurate measurements. The 

 slightest slip may mean an inaccurate 

 measurement and produce untoward results. 

 The mouth end and the pipeting finger 

 should be dry, otherwise, on measuring 

 small amounts, the delivery will be jerky 

 and usually unsatisfactory. 



4. After pipets have held infectious ma- 

 terial they should be placed at once in a jar 

 containing 1 per cent, formalin solution. 

 After pipeting blood, milk, or serum, the 

 pipets should be rinsed or placed in a jar 

 containing water or a weak lysol solution, as 

 the formalin solution tends to harden these 

 substances and renders cleaning quite diffi- 

 cult. They should be washed thoroughly, 

 the mouth end being plugged neatly and 

 firmly with a bit of cotton, and then placed 

 in a metal box or wrapped in newspaper and 

 sterilized in the hot-air oven. Unless all 

 the serum, blood, milk, etc., are well washed 

 out, the pipets may become occluded and 

 discolored. If this occurs, they should be 

 soaked for twenty-four hours in strong nitric 

 (50 per cent.) or sulphuric acid, and washed 

 thoroughly and sterilized. 



These pipets are gen- 

 erally used in immunologic 

 work. Note the small cotton plugs in the mouth ends. The 1 c.c. pipet (second from 

 the left) is graduated near to, but does not actually include, the tip; this feature is 

 highly desirable, as it permits measuring small amounts of fluid and the pipet is not 

 necessarily ruined, even though a portion of the tip were chipped off. 



