846 EXPERIMENTAL INFECTION AND IMMUNITY 



EXERCISE 26. PRECIPITINS (Continued) 

 EXPERIMENT 66. MILK-PRECIPITIN (LACTOSERUM) 



1. Secure a cubic centimeter of anticow serum previously prepared by immuniz- 

 ing rabbits with injections of fresti cow's milk. 



2. Prepare a 1:50 dilution of cow's milk (precipitinogen) by mixing 0.2 c.c. milk 

 with 9.8 c.c. normal salt solution. Prepare a similar dilution of human or goat milk 

 for control tests. 



3. Into a series of six small test-tubes place 2 c.c. of the following dilutions of 

 cow's milk: 1:50, 1:100, 1:200, 1:400, 1:800, and 1:1600. 



4. Into a second series of three tubes place 2 c.c. of the following dilutions of 

 control milk: 1:50, 1:100, 1:200. 



5. Into the nine tubes of these series add 0.1 c.c. cow lactoserum. 



6. A third series of six tubes containing 2 c.c. of the above dilutions of cow's 

 milk plus 0.1 c.c. of normal rabbit serum may be set up as further controls. 



7. Keep the tubes at room temperature and inspect at the end of fifteen min- 

 utes; half an hour; one hour, and two hours. 



(a) Describe a positive reaction. 



(b) Discuss the specificity of lactoserums. 



(c) Of what practical value are lactoserum reactions? 



EXPERIMENT 67. BACTERIAL PRECIPITINS 



1. Inoculate two flasks each containing 50 c.c. of sterile neutral bouillon with 

 cultures of Bacillus typhosus and Bacillus coli and cultivate at 37 C. for three weeks. 

 Filter cultures through a sterile Berkefeld filter until clear. 



2. Into a series of four small test-tubes place 2 c.c. of the following dilutions of 

 the typhoid filtrate (precipitinogen) undiluted: 1:2, 1:4, and 1:10. Prepare a 

 second series of tubes with similar amounts of the same dilutions of Bacillus coli filtrate. 



3. Add 0.1 c.c. of potent typhoid immune serum to all tubes of both series. A 

 serum with high agglutinin titer will be satisfactory. 



4. Place 2 c.c. of the undiluted typhoid and coli filtrates in separate tubes as 

 controls. Prepare an additional control by placing 0.1 c.c. of the typhoid immune 

 serum in 2 c.c. normal salt solution. 



5. Observe the tubes at the end of half an hour, and after one, two, and six 

 hours. 



(a) Describe a positive bacterial precipitin reaction. 



(b) Has a precipitate formed with the Bacillus coli filtrate? With 

 what microorganism would typhoid immune serum be likely to produce 

 a precipitate? 



(c) Discuss the relative delicacy of precipitation and agglutination 

 reactions in the differentiation of bacteria. 



EXPERIMENT 68. NOGUCHI GLOBULIN REACTION 



1. Secure 1 c.c. each of several cerebrospinal fluids from cases of paresis, tubercu- 

 lous meningitis, serous meningitis, and normal persons. 



2. Conduct this floccule-forming reaction after the technic given in the text. 



3. Make total cell counts on each fluid (see text). 



