Dec. i6, 1918 



Multiple-Pipette Holder 



617 



The pipettes are made of selected 4-mm. glass tubing and graduated 

 for the proper amount of serum for use in the test. These graduations 

 for convenience are etched at both ends. 



The bottles in which the serums are received, although varying slightly 

 in size and shape, have permitted the making of standard trays (fig. 2), 

 so constructed as to hold 144 bottles, 12 bottles wide and deep, and so 

 placed as to register with the pipettes when they are brought into 

 apposition. 



Each tray is numbered on the end to indicate its position in the test, 

 while the horizontal rows of bottles are given subnumbers to correspond 

 with their respective test-tube racks. The test tubes are numbered to 

 correspond with the bottles. 



The test-tube racks 

 (fig. 3) are constructed 

 to accommodate a 

 double row of 12 tubes 

 each and which, in turn, 

 register with the pi- 

 pettes. In short, the 

 arrangement of the 

 bottle trays, test-tube 

 racks, and pipettes is 

 standardized. 



When the stoppers 

 of the serum bottles 

 have been removed and 

 the trays arranged in 

 proper order to corre- 

 spond with the racks, 

 the operator is handed 

 one of the metal pipette 

 holders containing 1 2 

 clean, sterilized pi- 

 pettes. These are in- ' 



serted into the 12 bottles of the first row and immersed to just below the 

 surface of the smaller amount when suction is applied to the mouthpiece, 

 and serum from 12 test animals drawn up simultaneously by one 

 operation. The serums are drawn above the etched graduations, then 

 allowed to recede until the graduations are reached. This is done to 

 equalize the amount in each pipette, for it has been found that some 

 bottles contain more than others and when the serums are drawn up the 

 corresponding columns will be higher, but by letting the serum partially 

 escape down to the graduations, the quantities in the pipettes are readily 

 equalized. The serums are then transferred to the 12 test tubes bearing 

 numbers corresponding with those on the bottles. 



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Fig. 3. — Test tubes in rack. 



