The titration of diphtheria toxin by the flocculation method / A.T. Glenny and U. Wallace.

  • Glenny, A. T.
Date:
[1925?]
Catalogue details

Licence: In copyright

Credit: The titration of diphtheria toxin by the flocculation method / A.T. Glenny and U. Wallace. Source: Wellcome Collection.

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    antitoxin in use. For example, 1 unit of antitoxin containing 280 units per c.c. is delivered by each, quarter turn of a micrometer head attached to a syringe; delivering 0T c.c. for every seven turns. If enough syringes of suitable bore are not available the standard antitoxin is kept diluted down to a suitable strength. Thus we frequently use “8 turn’5 syringes with serum diluted to contain 200 units per c.c. One complete turn of the micrometer delivers 2*5 i units, or 1 unit is delivered by turning the fine adjustment through 20 divisions. The use of the micrometer syringe does not increase the time taken to prepare tj the tests when several series of tests are made with the same serum and the ' accuracy of manipulation is greatly increased. By adding very small volumes i of undiluted serum the total volume of liquid in each tube does not differ! sufficiently to affect the test. If the antitoxin is added in the form of larger;, volumes of diluted serum the total volume in each tube must be made equal. Table I. shows the typical method of titrating a toxin of unknown5 strength. A preliminary test (1) is made at very wide limits; to a series of 5 tubes each containing 1*0 c.c. of toxin we add 2, 5, 10, 20 and 50 units of antitoxin. In the particular example recorded we noticed after the mixtures had been kept at 50° for 25 minutes! that flocculation had occurred in the mixture containing 20 units of antitoxin (indicating mixture), but not in the tubes on either side, containing 10 and 50 units respectively (limiting values). From this I we concluded that the strength of the toxin lay between 10 and 50 Li units per c.c. The second test consisted of a series of 1 c.c. quantities of toxin to which were added 10, 15, 20, 30, 40 units of antitoxin In this series the mixture containing 30 units of antitoxin flocculated Table I. Typical titration of a toxin. Test .... l 2 3 4 5 Scale .... E D C B A Approximate differences between ioo% 50% 20% 10% 5% 1 successive mixtures. r 50- • • • 50- • • • 40- 40- • • • • • • 35- 30 + 30- 30- Number of units of AT. per c.c. of toxin. * • * 28- 26- 26- [ + — flocculation, - = no floccu-d ... 25 + 24 + 25 - lation at the time of ex- ... ... 24 - 1 amination (Tf).] • • • • • • 22 + 23+ j 22- > • • • • • • • • 21- 20 + 20- 20- 20- 20- i • • • 15- • • • • • • | V 10- 10- ... ... * * * Tf at 50° C. (in minutes) 25 24 20 18 ut Indicated value (in Lf units per 20 30 25 22-24 23 ! c.c.) Limiting values .... 10-50 20-40 20-30 20-26 22-24 -i