THE PHENOMENA OF INFECTION 463 



in the same way. Evidently the sensitizing group in the 

 protein molecule is a highly labile body and susceptible 

 to influences which so far we have not been able to recog- 

 nize. We have no difficulty in obtaining the poisonous 

 group uniformly, but it is otherwise with the sensitizing body. 

 Further work along this line is needed, and if an efficient 

 and uniformly reliable sensitizer for the tuberculous protein, 

 free from the poisonous group, can be secured, all children 

 should be vaccinated for tuberculosis; then with protection 

 against natural infection the restriction of tuberculosis 

 will be as completely under man's control as is that of 

 smallpox. It should be clearly understood that the pro- 

 tection afforded by vaccination is relative and not absolute. 

 The studies inaugurated by Wright have demonstrated 

 that vaccination is of service not only in prevention, but 

 also in cure. Bacteria and protozoa are particulate, and in 

 many diseases they are confined to limited localities. As 

 we have seen, sensitization may also be local. No body 

 cell is sensitized against a foreign protein until the latter 

 comes in contact with the former and penetration of the 

 body cell is probably essential to the most efficient sensi- 

 tization. The microorganisms of acne are located in the 

 cutaneous tissue, and being particulate and not in solution, 

 the area sensitized by them is small, if there be any sensiti- 

 zation at all. By vaccine therapy the area of sensitization is 

 greatly extended and the amount of lytic agent formed and 

 made available is greatly increased. This being in solution 

 and diffusible, digests and destroys the bacteria located in 

 the skin. The same is true of the treatment of localized 

 tuberculosis, or of any other localized infectious disease. 

 In vaccine therapy, as in vaccination, the great heed is for 

 soluble sensitizers free from poisonous content. When these 

 are secured, and not until then, we may develop a vaccine 

 therapy along scientific lines, and expect to secure important 

 results with it. 1 



1 The following pages are taken with but little change from an article by 

 Vaughan, Jr., in ".International Clinics." 



