304: INFECTION AND IMMUNITY 



the pipettes may be set on end in a tumbler and observed just 

 are the test tubes (Fig. 42, p. 340). The special methods of carrying 

 out agglutination tests with pneumococci have been described 01 

 p. 460. 



Precipitin Tests. In an earlier section on precipitins we hav< 

 seen that precipitates are formed when clear nitrates of bacterij 

 extracts or of both cultures are mixed with their specific immune 

 sera. Such precipitiii reactions are not limited to the realm oi 

 bacteria, but have a broad biological significance, in that specific 

 precipitating sera may be produced with proteins of varied source. 



For carrying out a precipitin test, the following reagents 

 required : 



1. A specific precipitating antiserum (antibacterial or antipi 

 tein) ; 



2. A bacterial filtrate or protein solution. 



PRODUCTION OF PRECIPITATING ANTiSERA. 1 Antibacterial pre- 

 cipitins may be produced in animals by a variety of methods. 

 Animals, preferably rabbits, are injected with cultures of the bac- 

 teria in gradually increasing quantities. Five or six injections are 

 given at intervals of from five to six days, the dosage and mode 

 of administration being adapted in each case to the pathogeiiicity 

 of the microorganisms in question. Myers 2 claims that specific pre- 

 cipitin for pepton in the culture media may be formed which may 

 lead to error. This could not be confirmed by Norris. 3 The im- 

 munized animals should be bled about 7 to 12 days after the last 

 injection. 



Precipitating antisera against protein solutions are prepared by 

 similar methods. Two or three injections, however, usually suffice. 

 The sera or protein solutions used should be sterile. This may be 

 accomplished by filtration through small porcelain filters. Injec- 

 tions into animals may be made subcutaneously, intraperitoneally, 

 or intravenously. The subcutaneous route has no advantages unless 

 the substances to be used are contaminated. It is far easier to 

 produce precipitating sera against proteins like horse serum, egg 

 albumin, etc., than it is to produce them against bacterial substances. 

 This is due probably to the fact that bacterial bodies contain rela- 





1 E. Kraus, Wion. klin. Woch., 1897; Norris, Jour. Inf. Dis., 1 and 3, 1904. 

 -Myers, Lancet, ii, 1900. 

 3 Norris, loc. cit. 



