382 SPECIFIC MICRO-ORGANISMS 



diagnostic, and the recognition of typical organisms in genital 

 chancres or lesions on the skin has important diagnostic value. 



Inoculation of animals is of little practical use in diagnosis, 

 but it has been possible by this method to demonstrate the fre- 

 quent presence of Sp. pallida in the circulating blood in cases of 

 untreated secondary syphilis. 



The detection of antibodies in the blood of the patient is under- 

 taken in two ways, first by the complement-fixation (Wassermann) 

 test and second by the luetin test. For the complement-fixation' 

 test, as performed at the Laboratories of the New York Post- 

 Graduate Medical School and Hospital the following are employed : 



1. The red blood cells are obtained by defibrinating fresh 

 sheep's blood, filtering it through paper if necessary to remove 

 fragments of clot, separating the cells in the centrifuge and wash- 

 ing them four times with 0.9 per cent salt solution. Finally i c.c. 

 of the corpuscles as packed by the centrifuge is suspended in 19 

 c.c. of 0.9 per cent salt solution; 0.2 c.c. of this suspension is 

 arbitrarily taken as the unit of red blood cells. 



2. The complement is obtained by drawing 5 to 10 c.c. of 

 blood from a large guinea-pig by cardiac puncture. This blood 

 is transferred to & Petri dish, allowed, to clot, incubated at 37° C. 

 for 30 minutes and then refrigerated. The separated serum is 

 then drawn oif with a pipette and 2 c.c. of it are mixed with 18 c.c. 

 of cold 0.9 per cent salt solution. This 10 per cent solution-.,of 

 guinea-pig's serum is kept in»a cold place, preferably immersed in 

 ice water. It is prepared on the day it is to be used. The unit 

 of complement is contained in o.i c.c. of this solution. Two 

 units ^©.2 c.c.) are employed in the actual test. 



3. The hemolytic amboceptor is prepared by injecting 2 c.c. 

 of tlioroughly washed (five times) sheep's corpuscles intravenously 

 into a large rabbit at intervals of three days, until four injectioils 

 have been given. Ten days after the last injection the animal is 

 allowed to fast for 12 hours and the blood is then asepticaUy 



1 Smith, J. W., and MacNeal: Jmirn. Immunology, 1916, 2, p. 75; Journ. Infect. 

 Diseases, 1917, 21, 233. 



