46 



MASS. EXPERIMENT STATION BULLETIN 319 



Table 15. — Behavior of normal parent strains and their variants in 



guinea pigs. 



Strain 



No. 



Pig Number of 

 No. Injections 



Symptomat ill igy 



Necropsy Findings 



Days after Isolation Agglutinin 



First of Titre 



Injection S. pullorum 



I-a 



VIII 



VIII- 



IX 



IX-a 



IX-b 



XVIII 



XVI I I-a 



Hi 

 17 



16 

 17 

 18 



[34 



35 

 36 



4 

 5 

 6 



[40 



VIII-c* 41 



42 



37 



Inactive, wea 



appetite on 

 Inactive, wea 



appetite on 



evidence of 



junctivitis 

 Inactive, weal 



appetite on 



evidence of 



junctivitis 

 Inactive, weal 



appetite on 



evidence of 



junctivitis 

 Inactive, weak and loss of 



appetite 



k and loss of 

 the 5th day 

 k and loss of 



the 4th day; 



purulent con- 



ik and loss of 

 the 5th day; 

 purulent con- 



ik and loss of 

 the 8th day; 

 purulent con- 



No symptoms 



Inactive, weak and loss of 

 appetite on the 4th day; 

 evidence of purulent con- 

 junctivitis 



No symptoms 



Inactive, weak and less of 

 appetite on the 2d day 



Inactive, weak and loss of 

 appetite on the 4th day 



Inactive, wea<£ ana loss of 

 appetite on the 4th day 



Inactive, weak and loss of 

 appetite on the 4th day; 

 evidence of p'urulent con- 

 junctivitis 

 Inactive, weak and loss of 



appetite on the 9th day- 

 Inactive, weak and loss of 

 appetite on the 10th day 



{Inactive on the 5th day 



No symptoms 



Inactive on the 6th dav 



No symptoms 



12 Not cultured 1:80 



7 Positive N. T.** 



21 



Positive 



Positive 



Negative 



N. T. 



N. T. 



1:1280 



*Apparentlv normal strain derived from VIII- 

 **N. T— no test. 



Summarizing briefly, it may be stated that the so-called normal type of 5. 

 pullorum, as described previously, possesses certain characters that have been 

 lost or modified in the variants derived from the normal parent strains. The 

 marked difference in virulence between the normal and the variant, as revealed in 

 the chick experiment, was also confirmed in the studies with the guinea pigs. 

 The variant was not only less invasive, but also less capable of establishing itself 

 locally in the host than was the parent strain. 



