UNDULANT FEVER 693 



the dry state in dust or on clothing for two to three months, in 

 tap- or sea-water for a month. The thermal death-point is about 

 55 C. 



Inoculated into animals no result usually ensues ; in the 

 monkey, however, a febrile condition is produced, with enlarged 

 spleen, sometimes terminating in death, the course of the tempera- 

 ture resembling that of the disease in man. By intra- cerebral 

 inoculation Durham found that the organism becomes pathogenic 

 for the rabbit and guinea-pig, otherwise it is without effect. 

 For the diagnosis of the disease the agglutination reaction is 

 most valuable. It may be carried out by the microscopic method, 

 a forty-eight-hours' broth culture being employed, the details of 

 the process being the same as described at p. 232. Dilutions 

 of 1 in 30, 1 in 50, and 1 in 100 should be prepared, as well as 

 controls with normal serum, for old laboratory strains sometimes 

 agglutinate with normal serum in dilution of 1 in 20 or 30. (Neglect 

 of this precaution led Bentley to ascribe kala-azar to a Malta 

 fever infection.) The organism being minute, it is necessary 

 to use the ^-in. oil immersion, the -in. with a high eyepiece and 

 draw-tube extended, or better, a J-in. dry objective. Bassett- 

 Smith 1 for agglutination tests prefers the sedimentation method, 

 for which an emulsion of a forty-eight-hour old agar culture in 

 physiological salt solution should be employed. Three dilutions 

 of the serum are made, 1 in 40, 1 in 100, and 1 in 400, and the tubes 

 are placed in the blood -heat incubator for two hours and the results 

 noted. The tubes should then be allowed to stand at laboratory 

 temperature and the results recorded after a further period of 

 twelve hours. In some 2,000 observations, only once was a 

 positive agglutination obtained with a control serum. Comple- 

 ment-fixation tests may also be employed and are satisfactory. 

 Absence of agglutination does not necessarily negative a diagnosis 

 of undulant fever : in cases of long duration it may be absent. 

 Isolation of the organism from the blood is another method that 

 may be used, but similarly may fail in long-standing cases. 



The disease may be conveyed to monkeys by contact, by 

 inhalation of infected dust, and by feeding. Mosquitoes and 

 other insects do not seem to convey it. 



The investigations of the Mediterranean Fever Commission have 



i Journ. ofHyg., xii, 1912, p. 497. 



