464 CHRONIC INFECTIOUS DISEASES 



may be introduced into the conjunctival sac with a camel- 

 hair brush. The reaction usually begins five to six hours after 

 the instillation of the mallein and lasts from twenty-four to 

 thirty-six hours. A positive reaction is manifested by an 

 accumulation of yellow exudate at the inner canthus of the 

 eye to which the mallein has been applied; In some cases 

 the discharge is very slight, in others profuse and usually 

 associated with severe conjunctivitis; at other times the 

 conjunctivitis is absent. The intensity of the reaction is not 

 an index of the extent of the disease. Ordinary mallein 

 used for subcutaneous testing is not adaptable. The Bureau 

 of Animal Industry prepares a special mallein for ophthalmic 

 tests, which contains no glycerin as a preservative. Some 

 experimenters have used dry mallein (mallein siccum). As a 

 rule positive reactions are not attended by fever or systemic 

 disturbances. Some glanderous horses, however, are so hyper- 

 sensitive to mallein that they give a thermic reaction. It 

 is therefore advisable to take the temperature just before 

 the mallein is instilled and again when the eye is being 

 examined to determine the reaction. When the reaction is 

 doubtful the complement-fixation test may be used as a 

 control. The test may be repeated within twenty-four hours 

 on the same, or control eye. If another retest is necessary 

 it should not be made in less than three weeks. 



3. The subcutaneous method is applied as follows: 



The normal rectal temperatures of the horse to be tested 

 are first determined one or two days before the injection of 

 mallein is made, best taking them each morning, noon, and 

 evening. 



The mallein is injected in doses of 1 c.c. into the side of 

 the neck. 



Beginning four to eight hours after the injection, the 

 post-injection temperatures are obtained every two hours 

 until the twentieth hour after injection, and carefully 

 recorded. 



Interpretation of Results. — A typical reaction consists in 

 an elevation of temperature of at least 3.6° F., and must 

 exceed 104° F. The temperature curve usually remains at an 

 elevation for some time, or it may make a slight drop and 



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