262 BACTERIA 



the inoculation is the apex of the shoulder, which has been 

 antiseptically cleaned. A mere prick is the whole operation. 

 After the first injection there is generally a definite febrile 

 reaction and a slight local swelling. From -^-^ or ^ cc. the 

 dose is steadily increased, until at the end of two or three 

 months ' perhaps as much as 300 cc. (or even half a litre) 

 may be injected without causing the reaction which the 

 initial injection of ^V cc. caused at the outset. This shows 

 an acquired tolerance of the tissues of the horse to the toxic 

 material. After injecting 500 cc. into the horse without 

 bad effect, the animal has a rest of four or five days. 



3. To Obtain the Antitoxin, During this period of rest 

 the interaction between the living body cells of the animal 

 and the toxins results in the production in the blood of an 

 antitoxin. By means of a small sterilised cannula, five, or 

 eight, or even ten litres of blood are drawn from the jugu- 

 lar vein of the horse into sterilised flasks or jars. The top 

 of the jar is closed by two paper coverings before it is 

 sterilised. Then it is again covered with a further loose 

 one. Before use the loose one is removed and replaced by 

 a metal (zinc) lid, which has been separately sterilised. This 

 metal lid contains an aperture large enough for the tube 

 which conveys the blood from the cannula to pass through. 

 The tube, therefore, passes through the metal lid and two 

 paper covers, which it was made to pierce. When enough 

 blood has passed into the vessel the tube is withdrawn, and 

 the metal lid slightly turned. Thus the contained blood is 

 protected from the air.* 



^ To shorten this period Dr. Cartwright Wood has adopted a plan by which 

 time may be saved, and 200 cc. injected say within the first two or three weeks. 

 This is accomplished by using a "serum toxin " (containing albumoses, but not 

 ferments) previously to the broth toxin, an ingenious method which we cannot 

 enter into here. 



^ At the conclusion of the operation the cannula is removed from the jugular 

 vein, ^nd the wound is closed by the valvular character of the slit in the skin 

 and vein and the elasticity of the wall of the vein. No stitching or dressing 

 is required. Indeed, it is striking to observe in the horse an entire absence of 

 pain throughout the proceedings. 



