108 BACTERIOLOGY 



fore, in the use of this agent, great care must be exercised 

 to avoid producing a reaction. The initial dose is, 

 therefore, placed very low. Thus, of old tuberculin such 

 a dilution is used as will give -nriinF nig- in each 2 minims. 

 Two minims of this dilution is mixed with sterile water 

 and injected with a hypodermic syringe under the skin 

 of the forearm or elsewhere, where it may be watched 

 for local reaction. The dose is increased by 2 minims at 

 a dose every four to eight days until 20 minims are in- 

 jected, when a stronger dilution is used, one containing 

 j-ffVr mg. to each 2 minims. After the injection the tem- 

 perature, pulse, and respiration are carefully watched 

 for signs of reaction. Should any occur, the next dose 

 is omitted and the following dose reduced. In this way 

 the patient's tolerance is carefully and gradually in- 

 creased until no untoward symptoms follow large doses, 

 i. e., as much as 200 mg. It will be seen that the tuber- 

 culin treatment, of necessity, must occupy an extended 

 period of tune, and, in fact, eight months to a year 

 should be occupied in carrying the patient through the 

 immunizing process. 



Small-pox Vaccine. Vaccine for small-pox was orig- 

 inated by Jenner in 1798. He observed that milkmaids 

 who had pustules upon their hands resembling those 

 upon the cows' udders were immune to small-pox. It 

 is, therefore, perhaps the oldest known application of 

 serum therapy. In principle it differs from all the later 

 biologic remedies. 



