112 VACCINE AND SERUM THERAPY. 



mococci, gonococci, streptococci, typhoid and dysentery bacilli, 

 cholera spirillae and many other microorganisms. Based on these 

 results, many different anti-bacterial sera have been used in passive 

 immunization in man. The results of anti-bacterial sera in the 

 treatment of diseases of man have, however, not been as satis- 

 factory as those obtained with specific anti -toxic sera. The im- 

 portance of complement has already been emphasized. There are, 

 however, other reasons why anti -bacterial sera have not yielded 

 as good results as anti-toxic sera. 



Anti -bacterial substances, with the aid of complement, have 

 the power of destroying bacteria but not of neutralizing bacterial 

 toxins. For this reason it is essential that anti-bacterial sera be 

 used early enough in the disease, before the bacteria have had a 

 chance to multiply v sufficiently and to set free enough poison to 

 injure and kill the cells. Early injection of specific sera unfortu- 

 nately is not possible in many of the diseases for which specific 

 anti -bacterial sera have been used, but as our methods of early 

 diagnosis are improved earlier administration of these sera will 

 be made. It is to be remembered that it is of the utmost impor- 

 tance that these sera be used before the infecting organisms 

 have multiplied greatly. 



Another reason of the failure of anti -bacterial sera to cure 

 disease is dependent upon the fact that as the bacteria are dis- 

 solved and destroyed by the action of immune substance and com- 

 plement, the intracellular toxins are liberated. If the body cells 

 are not able to cope with the increased amount of toxin liberated 

 upon the solution of the bacteria, they will die and the gravity of 

 the disease be increased. Hiss has produced evidence to show 

 that the leucocytes contain substances neutralizing these poisons. 

 To have liberated the minimum amount of toxin, anti-bacterial 

 sera should be administered when the number of invading bacteria 

 is relatively small, which will be early in the disease. 



Anti -bacterial sera are standardized with more difficulty and 

 less reliably than are the anti-toxic sera. Attempts have been 

 made to determine the number of smallest fatal doses of bacteria 

 a given amount of serum will 'protect against. It is to be remem- 

 bered, however, that with living microorganisms, a multiple of 

 the fatal dose is not as much more severe than a single dose as 



