920 EXPERIMENTAL INFECTION AND IMMUNITY 



3. Into a series of six small test-tubes place 0.1 c.c., 0.2 c.c., 0.4 c.c., 0.6 c.c., 0.8 

 c.c., 1 c.c. of the diluted immune serum; add 1 c.c. of suspension of blood-cells and 

 1 c.c. of salt solution to each tube. As a control, place 1 c.c. of corpuscle suspension 

 and 1 c.c. of normal salt solution into a seventh tube. 



4. Shake gently and place in the incubator for an hour. 



(a) Describe agglutination of red corpuscles. 



(b) Are the clumps easily broken up? 



(c) What would have occurred if complement were present? 



(d) Why was it necessary to heat the fresh immune serum? Is it 

 necessary to heat an old immune serum? 



(e) Examine a loopful of the sedimented corpuscles microscopically. 



EXPERIMENT 61. BLOOD TRANSFUSION TESTS 



Several students may contribute a few cubic centimeters of their blood and 

 agglutination and hemolysin tests made as described in the text (Chapter XVI). 



Of what value are agglutination and hemolytic tests -preliminary to 

 blood transfusion? 



EXERCISE 24. PRECIPITINS 

 EXPERIMENT 62. TITRATION OF A PRECIPITIN SERUM 



1. Secure 1 c.c. of antihorse immune serum prepared by immunizing a rabbit 

 with normal horse serum. 



2. Secure 1 c.c. of normal horse serum and place 2 c.c. of the following dilutions 

 made with normal salt solution into a series of six narrow test-tubes : 1 : 100, 1 : 500, 

 1:1000, 1:2000, 1:5000, and 1:10,000. 



3. To each tube add 0.1 c.c. of the immune serum. The tubes must not be 

 shaken. 



4. Place tubes in an incubator at 37 C. and observe every thirty minutes for 

 two hours and again after standing in a refrigerator overnight. 



(a) Describe the phenomenon of precipitation. 



(b) What are the requisites of a satisfactory precipitin serum? 



(c) What are the requisites of a satisfactory preparation of the 

 antigen for this reaction? 



(d) Discuss the delicacy of this reaction. 



EXPERIMENT 63. TITRATION OF A PRECIPITIN SERUM 



Repeat this titration, using antihuman immune serum and normal human 

 serum. 



EXPERIMENT 64. SPECIFICITY OF PRECIPITINS 



1. Secure 1 c.c. each of clear antihorse and antihuman serums. 



2. Secure 1 c.c. each of normal horse, normal human, and normal guinea-pig 



