904 EXPERIMENTAL INFECTION AND IMMUNITY 



tions are given. If possible, take temperature every four hours. Observe both 

 animals for symptoms of infection. If one or both succumb, autopsy aseptically and 

 culture the heart blood in neutral bouillon or bile. 



(a) Are there differences in the clinical condition of the two animals? 



(b) To what do you ascribe these differences? 



(c) What chief antibody is responsible for the destruction of the 

 bacilli in the immune animal? 



(d) Has typhoid bacteremia developed? 



PASSIVE ACQUIRED IMMUNITY 

 EXPERIMENT 27. ACQUIRED PASSIVE (ANTITOXIC) IMMUNITY 



1. Inject a 250- to 300-gram guinea-pig subcutaneously with 1 c.c. (500 units) of 

 diphtheria antitoxin (pig No. 1). 



2. Secure diphtheria toxin in which the lethal dose (L. D,.) for a 250- to 300-gram 

 guinea-pig is known. 



3. Place this dose of toxin in a small test-tube or, better, in the barrel of a pre- 

 cision syringe (Kitchens), and add 1 c.c. antitoxin (500 units). Mix thoroughly and 

 keep at room temperature for an hour. 



4. Inject pig No. 1 with an amount of toxin equal to the L. D. dose. 



5. Inject the toxin and antitoxin mixture into a second pig of 250 to 300 grams. 



6. Inject the same amount of toxin into a third pig of equal weight as a control. 



7. Observe animals closely for at least four or five days. 



(a) What are the chief symptoms of diphtheria intoxication of the 

 guinea-pig? 



(b) Do all animals show these symptoms? 



(c) How do you explain the absence of symptoms in pig No. 1? 

 How in pig No. 2 ? Is the mechanism of protection the same in both? 



(d) What bearing has this experiment upon the treatment of diph- 

 theria? 



EXPERIMENT 28. ACQUIRED PASSIVE (ANTITOXIC) IMMUNITY 



The above experiment may be conducted in exactly the same manner, using 

 tetanus toxin and antitoxin. 



EXPERIMENT 29. ACQUIRED PASSIVE (ANTIBACTERIAL) IMMUNITY 



1. Secure a culture of pneumococcus, and if its lethal dose for white mice is un- 

 known, determine this by injecting a series of mice with decreasing doses of a forty- 

 eight-hour serum bouillon culture. 



2. Secure a few cubic centimeters of antipneumococcus serum, especially a serum 

 prepared with the culture being used, or at least one that is polyvalent. 



3. Inject three mice subcutaneously with 0.1, 0.5, and 1 c.c. of the serum. Then 

 inject them subcutaneously with double the lethal dose of pneumococci. Inject a 

 fourth mouse with culture alone (control). 



4. Observe the animals for several days, and at autopsy culture the heart blood in 

 tubes of serum bouillon and prepare smears which are to be stained according to 

 Gram. 



