THE DETECTION OP BACTERIAL PATHOGENICITY 235 



wildly at loud noises or sudden motion. Constant pawing of the nose is 

 often indicative of infection of the upper respiratory system. A gasping, 

 spasmodic type of respiration can be seen in mice which are suffering 

 from pulmonary infection or irritation. 



In rabbits and guinea pigs the most helpful clinical sign is an elevation 

 of the temperature. It is always well to obtain a preinoculation tem- 

 perature on an experimental animal in order to establish his normal level 

 as well as to make certain that the animal is not suffering from some 

 intercurrent infection at the time it is first used. Animals which are 

 prostrated and about to die may very often have a subnormal tempera- 

 ture. An animal which is cold, either because it has a fever or because of 

 low temperature in its surroundings, may shiver. In rabbits and guinea 

 pigs diarrhea, snuffles, discharging eyes, and particularly encrusted con- 

 junctivae are aU indicative of ill health. 



When examining inoculated animals it is not sufficient merely to open 

 the cage and glance at the animals. Move the animal around in the cage, 

 or in the case of mice, pick them up with a forceps and permit them to 

 move about on the wire-screen top of the box. Frequently an animal 

 which appears to be perfectly well when left alone Avill be found to be 

 lethargic, paralyzed, or trembhng when disturbed. 



RECOVERY OF BACTERIA FROM INFECTED ANIMALS 



It not infrequently happens that an entirely different organism is 

 isolated from an animal which has been previously inoculated with some 

 known strain. For example, Pasteurella lepiseptica can readily be iso- 

 lated from rabbits injected with suspect acid-fast or mycotic agents. 

 Thus, before proceeding with either an animal autopsy or removal of 

 serum or exudates from an infected species, it is always well to consider 

 beforehand the precise procedures which mil be taken, to collect all the 

 necessary materials and instruments, and, w^hen the operation is com- 

 pleted, to prepare proper and adequate notes. Certain laboratory equip- 

 ment should be maintained in readiness and preferably in one particular 

 portion of the laboratory for animal-autopsy work. The bacteriologist 

 should bear in mind that the recovery of microorganisms from experi- 

 mentally infected animals can be one of the most hazardous operations in 

 bacteriology. 



Procedures will vary in different laboratories, but in general it is well to 

 have a large covered container of IIgCl2 or similar germicidal solution, 

 large towels which can be placed in the germicide before and after comple- 

 tion of the procedures, a set of sterile instruments, bunsen burner, 

 sterihzers, and sterile glass pipets, cotton, and similar materials for 

 removal of exudates. It is a good general policy to employ an assistant, 



