616 SUMMARY OF CURRENT RESEARCHES RELATING TO 



cannot be included in the biological factor limiting the number of 

 bacteria in soil. 



Russell points out that these organisms are in the main those which 

 figure largely in cultures made by adding soil to hay infusions, and that 

 there is no evidence that the normal soil fauna were put back into the 

 partially sterilized soil, nor that the added organisms survived at all. 

 .Moreover Goodey did not appear to have overcome the great difficulty 

 of securing an adequate control. When a soil is partially sterilized by 

 heat, antiseptics, or prolonged storage, other changes are produced 

 besides the destruction of the limiting factor and the protozoa. Some 

 ammonia is formed and the amount of soluble matter is increased — 

 both evidence of a change in soil constituents— and within a few days 

 after remoistening, great numbers of bacteria and of their decomposition 

 products accumulate. Hence by adding protozoa to (a) untreated soil 

 containing normal numbers of bacteria and protozoa, and {b) partially 

 sterilized soil, changed somewhat, and containing abnormal numbers of 

 bacteria and their products, the organisms in the second case are placed 

 under unfavourable conditions for development ; in addition to this the 

 added protozoa are contaminated with hay infusion and bacteria. 

 Hence no clear issue is obtained between soil protozoa on the one 

 hand and soil bacteria on the other. 



Etiology of Typhus Fever.*— H. Plotz, P. K. Olitsky and G. Baehrf 

 record the isolation of a bacterial organism which they have regarded as 

 the causal agent of typhus fever. The bacterium in question is a strict 

 anaerobe, and was first isolated by the application of Nuguchi's methods 

 for the cultivation of spirochetes. The best growth, however, was 

 obtained on serum glucose agar, on which it forms opaque rounded 

 colonies at a depth of 3 cm. or more below the surface of the medium. 

 The organism is small (0 ■ 9-1 ■ 98 /x in length), pleomorphic and Gram- 

 positive. It is non-motile and non-acid-fast and has no capsule. It 

 may be straight or slightly curved, witli rounded or slightly pointed 

 ends. Coccoid forms are also met with, and involution forms occur early ; 

 spores do not occur. It ferments glucose, maltose, galactose and inuliu 

 with production of acid without gas. Growth in artificial media is slow. 

 The reaction of agglutination and fixation of complement are present 

 when the organism is brought into contact with a specific serum, and 

 precipitation occurs in a mixture of such serum and bacillary extract. 

 Monkeys are readily susceptible to typhus infection, which can be in- 

 duced by injections of a patient's blood both before and after the crisis. 

 The organism has been named Bacillus typhi exanthematici, at the sugges- 

 tion of W. H. Welch, the name having been originally suggested by 

 Klebs for the hypothetical infective agent of the disease. 



Destruction of Locusts by Biological Means. $ — F. d'Herelle 

 has previously described a method of destroying locusts by means of 

 insufflations of cultures of Coccobacillus acridiorum, the causal organism 



* Lancet (1915) ii. pp. 876-7. 



t Journ. Infect. Diseases, xvii. (1915) No. 1, pp. 1-68. 



\ Comptes Eendus, clxi. (1915) p. 503-5. 



