480 EXPERIMENT STATION RECORD. [Vol.40 



a diagnosis based on characteristic lesions they should be killed later, prefer- 

 ably aft en seven or eight weeks. 



The survival of the hog-cholera virus in laboratory animals, particularly 

 the rat, C. TenBeoeck (Jour. Expt. Med., 28 (1918), No. 6, pp. 749-757).— This 

 is a report of an investigation of the effect of hog-cholera virus on various 

 laboratory animals. The method employed was to inoculate several animals 

 of a given species in one or more ways, and after seven days to determine 

 whether the virus was still present in their bodies by inoculation of suseeptihle 

 pigs. 



Attempts to demonstrate the virus of hog cholera after intravenous and 

 intra-abdominal inoculations were unsuccessful in the case of rabbits, guinea 

 pigs, and pigeons. It was proved, however, that the virus can be found in the 

 bodies of white rats for at least seven days after either intra-abdominal or 

 intracerebral inoculations. Passing one strain of virus alternately through 

 pigs and rats for three transfers in each species did not change the virulence 

 for swine nor cause the virus to become virulent for rats. Attempts to Intro- 

 duce the virus into the body of the rat by feeding virulent material ami an 

 attempt to pass the virus through one lot of rats i.i another were unsuccessful. 



From these observations the conclusion is drawn thai the rat does nut play 

 a part in the transmission of bog cholera. 



A study of paratyphoid bacilli isolated from cases of hog cholera. <\ Ten- 

 Broeck (Jour, h'.rpt. Med., 28 (1918), X<>. 0. pp. 759-777).— During the COUTSe of 

 experimental work on hog cholera, paratyphoid bacilli were isolated from 16 

 per cent of the hogs. Culturally these organisms were found to be the same as 

 paratyphoid bacilli isolated from man and different in many respects from 

 hog cholera bacilli. In their agglutination in sera produced by the injection 

 of living cultures one of the cultures corresponded to Bacillus enteritidit, 

 while live apparently formed a class by themselves, resembling paratyphoid H 

 more t-losely than hog cholera bacilli, but different from both in the type of 

 clumps formed and in absorption experiments. When injected into rabbits 

 they produced an immunity to the hog cholera bacillus, while paratyphoid B 

 does not. 



The author considers it probable that s-ome of the cultures that are described 

 as hog cholera bacilli belong to this group. Whether the ingestion of pork con- 

 taining these bacilli would cause disease in man has not yet been determined. 



A study of the changes in virulence of the pneumococcus at different 

 periods of growth and under different conditions of cultivation in media, 

 A. B. WadSWOBTH ami M \uy B. Kirkhkidf: (Jour. Expt, Mel.. ..'* i /.''/*). Xo. 6, 

 pp. 791-805). — In this paper are presented the results of a preliminary study 

 of the essential relation between the different phases of growth and the degree 

 of virulence of the pneumococcus. 



It wns found possible, by rapid transfers alone, not only to maintain the 

 virulence for mice of the pneumococcus in artificial media, but also to restore 

 a certain degree of virulence to cultures previously rendered avirulent by 

 less rapid transfers in the same medium. For these results the presence of 

 enriching Quids such as blood or serum was not required. Attenuated cultures 

 which had been shown to be avirulent for mice at the 24-hour period of growth 

 exhibited marked pathogenicity if injected during or especially at the com- 

 mencement of the period of maximum growth, when the growth energy may be 

 considered at its height. 



The authors consider it Improbable that the close relation between the \ 

 tative power or growth energy of the pneumococcus- and its pathogenic power 

 is peculiar to this organism, but that it forms the basis not only of the essen- 



