Measurement of Vitamine Content. 123 



authors but seems to permit of better control and to be at the 

 same time more easily handled than the Williams method. This 

 method is presented herewith, not as a finished product for we are 

 still experimenting with certain details of standardization, but 

 with a view to stimulating criticism and suggestion. 



The Bachman test measures the vitamine activity in terms 

 of gas generated ; it is really a measure of enzyme activity. This 

 fact makes it difficult to be sure that the stimulus is a growth 

 stimulus or merely an enzyme control in any given test. The 

 Williams test measures the effect of the vitamine in growth of 

 yeast cells and this seems to us a more reliable indicator than the 

 gas production. On the other hand the hanging drop method of 

 Williams makes difficult the control of concentration during 

 incubation and we found the preparation of drops containing single 

 yeast cells far from easy to prepare. We believe that our method 

 obviates both these difficulties while retaining the yeast cell count 

 as an indicator. 



The Method. — The illustration shows the tools used, being 

 essentially those of the opsonin technique. The first step is the 

 preparation of two capillary pipettes by drawing out in the flame 

 a 5 mm. glass tube as shown in A. This tube is marked at the 

 center with a pen point (1) and with the aid of a drop of mercury 

 accurately calibrated into units of equal volume on each side of 

 the center point (2) and (3). The two halves are then separated 

 at the point (1) into two pipettes. Each pipette is then heated 

 at the large end and a constriction made to permit a flame seal 

 later, the end plugged with cotton and the pipette sterilized. 

 After sterilization and by fitting a rubber bulb to the end as in B 

 the pipette is ready for use. After filling as described below the 

 tip and constriction point are sealed in the flame and the tube is 

 ready for incubation, C. 



The materials necessary for the test are the pipette described 

 above, a dilute suspension of yeast cells in Nageli solution, and 

 the vitamine extract to be tested. These are prepared as follows: 

 A pure culture of Fleischman round yeast is maintained on an 

 agar slant. Two days before the test a transfer is made to a fresh 

 slant and in all our tests, cells of 48 hour growth are used. From 

 such a slant the smallest amount of yeast that can be taken up on a 



