912 EXPERIMENTAL INFECTION AND IMMUNITY 



(a) Define the unit of diphtheria antitoxin. 



(b) Of what practical value is the measurement of diphtheria anti- 

 toxin? 



(c) Is there any practical method of determining the quantity of 

 toxin in the blood of a diphtheric patient? 



(d) How would you determine the amount of natural antitoxin in 

 the blood of a person? 



EXPERIMENT 45. STANDARDIZING TETANUS ANTITOXIN 



The technic of standardizing tetanus antitoxin may be carried out in a similar 

 manner with dried Standard Toxin and an antitoxin purchased in the open market. 



EXERCISE \ 7. ANTITOXINS (Continued) 

 EXPERIMENT 46. SPECIFICITY OF ANTITOXINS 



1. Secure small quantities of fresh diphtheria and tetanus toxins; the L+dose 

 of each should be known. 



2. Secure small quantities of diphtheria and tetanus antitoxins; the number of 

 units per cubic centimeter of serum should be known. 



3. Into four precision syringes place the following mixtures. After standing an 

 hour at room temperature, inject subcutaneously into 300-gram guinea-pigs. 



No. 1: L+dose of diphtheria toxin +100 units of diphtheria antitoxin. Inject 

 into pig No. 1. 



No. 2: L+ dose of diphtheria toxin +100 units of tetanus antitoxin. Inject into 

 pig No. 2. 



No. 3: L+dose of tetanus toxin +100 units of tetanus antitoxin. Inject into 

 pig No. 3. 



No. 4.: L+ dose of tetanus toxin+100 units of diphtheria antitoxin. Inject into 

 pig No. 4. 



(a) What do you observe regarding the specificity of antitoxins? 



(b) What are the main symptoms of diphtheria and tetanus in the 

 guinea-pig? 



(c) Even though a pig injected with diphtheria toxin shows no gen- 

 eral symptoms of intoxication, what local sign may be present? 



(d) What is the nature of the toxin-antitoxin reaction? 



EXPERIMENT 47. NATURE OF THE TOXIN-ANTITOXIN REACTION. 

 ACTION OF ANTI-TETANOLYSIN 



1. Secure fresh tetanus toxin and determine the dose producing complete hemoly- 

 sis of 1 c.c. of a 1 per cent, suspension of rabbit corpuscles in two hours at 37 C. 



2. Place double this dose of toxin in a series of six small test-tubes and add in- 

 creasing doses of fresh tetanus antitoxin: 0.001 c.c., 0.005 c.c., 0.01 c.c., 0.05 c.c., 

 0.1 c.c., 0.2 c.c. Add salt solution to bring the total volume to 1 c.c. ; incubate at 37 C. 

 for an hour. Add 1 c.c. of 1 per cent, suspension of rabbit corpuscles to each tube. 

 Prepare two controls, one with the dose of toxin and corpuscles but to which no serum 



