1897J MTCROSCOPICAL JOURNAL 57 



hands liigli, from 1,400 to 1,600 })(>iiiids weiglit, of quiet 

 disposition, iind possessing good health. 



TESTING FOR (iLANDERP AND TUBERCULOSIS. 



Before the injecting with toxin, the malleine test for 

 glanders and the tuberculin test for tuberculosis is ap- 

 plied, the results of such being clearly shown by the tern- 

 [)er?iture. Animals responding to either of these tests 

 must be discarded. 



The primary injection of the toxin is 1 ccm. At equal 

 periods of from six to eight days, constantly increasing 

 amounts of the toxin are administered until in about ten 

 weeks to tliree months as great quantities as 300 ccm. of 

 this powerful toxin may be borne with tolerance. 



When the injection of these larger amounts is accom- 

 panied with but little elevation of temperature, and but 

 a slight oedema is manifested at site of injection, a trial 

 bleeding is made, 20 ccm. of blood being taken from the 

 jugular. If the tests for antitoxic value, as described 

 later under the testing of antitoxin, are favorable, the 

 horse is bled, the blood being collected in sterile bottles, 

 and placed in a refrigerating room for a sufficient time 

 (about 24 hours) until the fibrin coagulates, allowing the 

 serum which contains the antitoxin to remain clear. This 

 serum is drawn oft' by pipettes and preserved by the ad- 

 dition of 0.5 per cent trikresol. 



The most important step now awaits the operator, the 

 determination of the exact strength possessed by the 

 antitoxin as expressed in immunizing units. 



THE IMMUNIZING UNIT. 



Immunizing units represent the strength of antitoxic 

 serum that is required to save a guinea pig from ten 

 times the absolute minimum fatal dose of the diphtheria 

 toxin, and the strength of the antitoxin is designated by 

 the number of immunizing units per ccm. of the serum. 



For this purpose the minimum fatal dose of the toxin is 



