488 IMMUNITY. 



showed that in cases treated on the first and second days 

 of the disease the mortality was only 7.3 per cent, and 

 this has been generally confirmed. After the fifth day it 

 is of little service to apply the treatment. In order to 

 obtain such results it cannot be too strongly insisted on 

 that attention should be given to the dosage. When bad 

 results are obtained it may be strongly suspected that this 

 precaution has not been observed. In the treatment of 

 acute tetanus by the antitoxine the improvement in results 

 has not been marked, but some chronic cases have been 

 benefited. Recently there has been practised with slightly 

 more hopeful result a drop by drop injection (repeated 

 daily if necessary) of from 2^-10 c.c. of antitoxine into the 

 substance of the frontal lobe by a syringe inserted through 

 a dental drill hole over the frontal eminence. In the case 

 of Yersin's anti-plague serum, though benefit has appeared 

 to follow its use, experience with its effects has been too 

 limited to enable a judgment to be formed. The same 

 may be said to be true of the antistreptococcic and anti- 

 pneumonic sera, and also of antivenene, though in the 

 case of the first mentioned numerous cases of apparently 

 successful result have been recorded. 



Theories as to Acquired Immunity. 



The advances made within recent years in our knowledge 

 regarding artificial immunity and the methods by which it 

 may be produced have demonstrated the insufficiency of 

 various theories which had been propounded. They also 

 show the futility of attempting, even now, to make a general 

 statement which would be applicable to all cases. One or 

 two of these theories may, however, be mentioned, as they 

 are of interest in connection with the development of this 

 subject. 



i. The Theory of Exhaustion, with which Pasteur's name 

 is associated, supposes that in the body of the living animal 

 there are substances necessary for the existence of a par- 

 ticular organism, which become used up during the sojourn 



