26 PROTEIN POISONS 



soluble proteins, but the distribution is more prompt and 

 effective with soluble than with particulate proteins. This 

 explains why the former are more efficient sensitizers than 

 the latter. It will be understood that a protein relatively 

 insoluble in vitro may become more readily soluble in vivo. 

 15. Vaccines are protein sensitizers. One of the most 

 important problems in scientific medicine now awaiting 

 solution is that of the preparation and employment of 

 vaccines. The term vaccine from vacca, a cow was 

 first used when Jenner employed the infection of cowpox 

 to induce immunity to smallpox. Since that time the use 

 of the word "vaccine" has been extended to include every' 

 form of preventive inoculation. Through the researches 

 of Wright vaccine therapy has been developed, and now 

 vaccines are employed not only in the prevention but in 

 the treatment of disease. Under 11 we have spoken of 

 the employment of vaccines in inducing immunity, and 

 now we wish to speak briefly of vaccine therapy. As we 

 understand it, these two uses of vaccines depend upon the 

 same principle. The action of the vaccine is the same in 

 both instances. The protein of the organism responsible 

 for the diseased condition and that of the vaccine must be 

 identical or closely related bodies. Both must be protein 

 sensitizers. In most, if not in all, of the systemic infectious 

 diseases the infecting organism sensitizes the body either 

 throughout or over large areas. It seems to us to treat 

 such diseases with vaccines is irrational, and we believe 

 that much harm has been done by such attempts. There 

 are, however, local infections in which the area of sensitiza- 

 tion is limited and circumscribed. Such diseases may be 

 treated rationally with vaccines, provided such agents 

 can be obtained in such forms that they will act both 

 effectively and harmlessly. The future of vaccine therapy, 

 in our opinion, depends upon our ability to secure such 

 vaccines. That we have not yet fully established our 

 ability to obtain vaccines that are both harmless and 

 effective we are ready to admit. This does not mean, 

 however, that all efforts to accomplish this should be dis- 



