14 



MASS. EXPERIMENT STATION BULLETIN 319 



Table I. History of the Newly Isolated Variants 



0.9 per cent NaCl solution which contained 0.5 per cent phenol. In three instances 

 the salt concentration was lowered to 0.22 per cent, in order to reduce the instability 

 of the strain in saline solution. It had been observed previously that these three 

 strains (9, 11, and 13) were salt sensitive. The concentration of the antigens 

 was adjusted to the desired turbidity, which in the final serum -antigen mixture 

 was equivalent to tube number 1.0 of McFarland's nephelometer scale. All 

 strains produced a uniform, homogeneous turbidity, with the exception of No. 8, 

 the suspensions of which appeared slightly clumpy. 



The results in Table 2 show that the different strains do not behave alike as 

 antigens in the presence of positive and negative sera and in 0.9 per cent saline 

 solution. In the majority of the antigens it was difficult to determine whether the 

 cells were agglutinated. Stable, well-defined clumps of cells were not visible to 

 the naked eye, as one ordinarily observes in typical agglutination with 5. pullorum. 

 However, even with a so-called typical pullorum antigen, one may observe 

 more than one type of agglutination. This fact is well brought to light when 

 numerous agglutination tests are recorded in the routine testing of fowl sera. 

 Arkwright (1930) stated that specific and non-specific agglutination of bacteria 

 is a phenomenon governed by conditions which belong to the realm of colloidal 

 physics and which are imperfectly understood at the present time. When old 

 cultures containing autolyzed or fragmented bacterial cells are suspended in salt 

 solution they may cause a precipitate. Under certain conditions the precipitating 

 substance may entangle the bacterial bodies, producing a reaction that can not in 

 reality be considered identical with true agglutination brought about by properly 

 sensitized intact bacterial cells suspended in a suitable electrolyte solution. 

 A comparable phenomenon is frequently observed when substances of a lipoid 

 and protein nature are precipitated under certain conditions, bringing down the 

 bacterial cells with the precipitating material. 





