92 BACTERIOLOGY 



diphtheria, the germ having been carefully killed and 

 removed from the toxin before its use. The effect of 

 the injection of the toxin bears out the statement made 

 earlier in this work that the symptoms arising from in- 

 fection with the various disease germs were due to the 

 toxins produced by the germ, rather than to the presence 

 of the germs themselves in the tissues of the infected 

 animal. 



Selection and Care of Horse. The horse is selected for 

 the production of an antitoxin because he is naturally 

 relatively immune to diphtheria, as well as tuberculosis 

 and other diseases, and furnishes a large quantity of 

 serum. Only healthy animals are selected. They are 

 tested for glanders with mallein, and kept constantly 

 immunized to tetanus by injections of tetanus antitoxin. 

 They are carefully cared for and every precaution exer- 

 cised to keep them in perfect health. 



After the horse has ceased to react to further injec- 

 tions of toxin, he is bled. He is prepared as for a sur- 

 gical operation. Covered with a sterile sheet, taken into 

 a specially prepared operating-room, where, under the 

 strictest aseptic precautions, the jugular vein is opened 

 and from 3 to 5 quarts of blood removed and received in 

 a covered sterile jar, which is placed in a special room and 

 allowed to clot, when the serum which contains the anti- 

 bodies can be separated from the clot or fibrin and red 

 corpuscles. After a few days' rest the horse is ready for 

 further toxin administration. 



