38 MASS. EXPERIMENT STATION BULLETIN 319 



markings. Smears from the different colonies showed the cells from liver infusion 

 agar cultures to be much larger than those taken from meat extract agar. In some 

 cases the difference was so great that the two cultures might be considered differ- 

 ent species. (See Figures 60-63, inclusive.) 



Strain 18,292 was recovered from all of the seven infected chicks. Gross lesions, 

 which were quite extensive in some cases, were present in all chicks. The colonial 

 and cellular types were similar to those observed with Strain 11,706. 



Antigens prepared from the isolated strains were agglutinated by positive 

 pullorum serum, but not by negative serum. However, four antigens (one pre- 

 pared from Strain Vl-a, and three from Strain XIV) exhibited atypical agglu- 

 tination. 



Blood samples were collected from all killed chicks. Agglutination tests with 

 pullorum antigen produced complete agglutination in dilution of 1:40, and a 

 trace in 1:80. 



No. 3. Variant IX-b was passed through five different groups of chicks by 

 serial passage. In the first passage a suspension of the organism with a turbidity 

 equal to tube 2 of McFarland's nephelometer scale was administered per orem 

 on three successive days in the following doses: — 0.2 cc, 0.5 cc, and 0.5 cc. 

 The remaining groups of chicks were inoculated subcutaneously with 0.4 cc. of a 

 suspension having the same concentration. The time during which the organism 

 remained in artificial cultivation varied between passages. Between the first and 

 second passages the organism was maintained in fresh egg yolk for twenty days 

 before being re-inoculated. In the remaining passages the primary culture was 

 two to five days old when inoculated. Table 11 shows the results of the serial 

 passage of this strain through chicks. The percentage of recovery of the organism 

 is low in every group except No. III. The organism recovered resembled the 

 original inoculated variant in every case. (See Figures 14 and 15.) Scattered 

 isolated colonies attained a diameter of approximately two centimeters. It 

 appeared as if the freshly isolated culture possessed some growth property which 

 appeared absent in the same variant maintained under continual artificial 

 cultivation. The cellular morphology did not vary to any degree during this 

 series of passages. 



Table 11. — Results of serial passage of variant IX-b through chicks. 



It will also be noted in Table 11 that the majority of isolations were made from 

 necrotic tissue located at or near the site of inoculation. The amount of necrotic 

 tissue and local tissue reaction varied greatly in the different chicks. In some 

 instances a proliferation of connective tissue, greatly congested and surrounding 

 the leathery yellowish necrotic material, was observed. In two instances the 

 organism invaded the tissues of the host beyond the point of inoculation. However, 

 it was apparent that the invasive power of the organism was not great, although it 



