440 THE SALMONELLA GROUP 



proves fatal : the symptoms are the same as, and post mortem the lesions are 

 identical with, those found in the spontaneous disease. A like result follows 

 if swine be fed with food which has been mixed with a large quantity up to 

 a litre of a young culture of a recently isolated strain. 



There are, however, essential differences between the disease produced by the 

 inoculation of the aertrycke bacillus (bacillus suipestifer) and the spontaneous dis- 

 ease of hog cholera. In the latter the disease is transmissible from the sick to the 

 healthy, the blood is infectious, and if the animal recover, it is permanently immune 

 in a high degree : in the former all these characteristics are absent ; the explanation 

 being that the spontaneous disease is caused by a filtrable virus with which the 

 bacillus aertrycke (suipestifer) is associated merely as a secondary infection. 



Sheep, cows and calves can only be infected by intra-venous inoculation. 



SECTION II. MORPHOLOGY. 



1. Microscopical appearance. The bacillus aertrycke has the microscopical 

 appearances and staining reactions common to the members of the typhoid- 

 colon group. In tissues and infected fluids the bacillus is always non-motile, 

 but in broth, agar or gelatin cultures it is highly motile and has four to seven 

 flagella (Ferrier). 



Metchnikoff has drawn attention to the marked pleomorphism of the 

 aertrycke bacillus and has pointed out that in cultures long filaments as 

 well as cocci sometimes arranged in chains are seen, in addition to the 

 typical cocco-bacillary forms. 



2. Cultural characteristics. The cultural characteristics of the aertrycke 

 bacillus are identical in every respect with the paratyphoid B bacillus and 

 with the gaertner bacillus. 



SECTION III. BIOLOGICAL PROPERTIES. 



1. Vitality and virulence. The aertrycke bacillus retains its vitality and 

 virulence in cultures for several months. 



Cornil and Chantemesse obtained an attenuated bacillus by exposing a 

 culture to a temperature of 43 C. for 90 days. The virulence of such an 

 attenuated strain may be restored to normal by passing it through a series 

 of rabbits ; moreover the virulence of a normal strain may be raised to a 

 very high degree by passage through a series of pigeons. 



The bacillus is killed by heating it at 54 C. for 40 minutes (Selander). In 

 brine it appears to be capable of living for a considerable length of time 

 (Savage). 



2. Biochemical reactions, (a) Action on carbohydrates. The changes 

 produced by the aertrycke bacillus when grown in media containing various 

 carbohydrates are the same as those produced by the paratyphoid B and 

 gaertner bacilli. 



(b) Indol. The aertrycke bacillus produces no indol in peptone water. 



3. Vaccination. Cornil and Chantemesse vaccinated rabbits by inoculating 

 them with their attenuated cultures : MetchnikofE immunized rabbits by 

 inoculating small doses of the virus. 



The inoculation of swine with pure cultures of the bacillus produces no 

 immunity .(Dorset, MacClintock), or merely a transitory immunity (Lourens) 

 against hog cholera. 



4. Toxins. In the tissues of inoculated animals the aertrycke bacillus 

 produces a very powerful toxin (Selander). 



The blood of rabbits which have succumbed to inoculation of a virus of 



