184 THE MICROSCOPE. Dec. 



The toxicity of the toxin is detenniaed by its injection 

 into guinea pigs, and tot)e of a desired strength, 0.01-0.1 

 ec. should produce death of the control animal in from 

 24 to 36 hours. 



For the preparation of diptheria antitoxin any animal 

 may be selected, but horses are preferred, inasmuch as 

 they are more easily operated upon, and because they 

 furnish excellent serum in liberal qu intities. Oar exper- 

 ience, as to the type of horse selected, particularly in the 

 earlier (»bservations has been valuable, being of unusally 

 good quality, a number showing trace of fine breeding ; 

 such horses however, are not suited for immunization, 

 the finely bred horse being sensitive, frets at his inac- 

 tivity (for no work is performed by the animal while being 

 immunized, only a sufficient amount of exercise being 

 given to maintain good health) neither does he take 

 kindly to the injection of the toxin, or the subsequent 

 bleeding operations. The preference is given to large, 

 compactly built animals of dark color, 16 to 18 hands 

 high, from 1400 to 1600 pounds weight, of quiet dispo- 

 sition and in good health. 



Before injecting with toxin, the mall^in teat for glan- 

 ders, and the tuberculin test for tuberculosis is applied, 

 the results of such being clearly shown in the tempera- 

 ture, which is carefully recorded. Animals responding to 

 either of these tests must be discarded. 



The primary injection of the toxin is 1 cc. and in equal 

 periods of from six to eight days, constantly increasing 

 amounts of the toxin are administered until in about ten 

 weeks to three months, as gr^at quantities as 300 cc. of 

 this powerful toxin may be borne with tolerance. When 

 the injection of these larger amounts is accompanied with 

 but little elevation of temperature, and but a slight oed- 

 ema is manifested at site of injection, a trial bleeding of 

 20 cc. of blood is made, the blood always being taken 

 jrom the jugular vein. If the tests for antitoxic value, 



