TOXINS. 181 



are carefully groomed and nourished and given 

 such exercise as will keep them in a healthy con- 

 dition. 



The toxins, in solution, are injected subcutane- 

 ously. 3 Grave and even fatal reactions may follow 

 the first injections, if the toxin, has been given in 

 too large doses or in too concentrated solutions. 

 This is especially true when injecting tetanus 

 toxin. It is of great importance first to establish 

 what the Germans call a "Grundimmunitat" 

 which means a primary immunity in the animal 

 itself so that the immunization may then be 

 pushed vigorously until the blood contains anti- 

 toxin in high concentration. For this purpose it 

 has been found necessary to weaken the first tox- 

 ins injected. This may be done by heating the 

 toxin solution to 65 or 70 C. for an hour; by add- Atteniiatlon 

 ing to it from 0.05 to 0.4 per cent, of the trichlo- * Toxins. 

 rid of iodin ; or by adding a solution of potassium 

 iodid in which iodin has been dissolved (Lugol's 

 solution) or, as is often done at present, by par- 

 tially neutralizing the toxin with antitoxin. High 

 dilutions of the unaltered toxin may also be used. 

 Gradually the virulence and amount of the toxin 

 injected may be increased until finally the full 

 virulent toxin is given in large doses. The increase 

 in dosage must be very gradual. Eventually as 

 much as a liter or more of diphtheria toxin is 

 tolerated. 



Following each injection a reaction occurs. 

 With diphtheria the local swelling may be great, 

 and sloughing may occur. Following an injection 



3. For the production of antivenin the snake venom Is 

 best injected intravenously. 



