556 IMMUNITY 



the power of which has been weakened by various methods (vide 

 infra). Afterwards the doses are gradually increased. This 

 method was carried out with a great degree of success in the 

 case of diphtheria, tetanus, malignant oedema, etc. It appears 

 capable of general application in the case of organisms where it 

 is possible to get an active toxin from the filtered cultures. It 

 has also been applied in the case of snake venoms by Calmette 

 and by Fraser, and a high degree of immunity has been 

 produced. 



The following may be mentioned as some of the most 

 important examples of the practical application of the principles 

 of active immunity, i.e., of protective inoculation : (1) Inocula- 

 tion of sheep and oxen against anthrax (Pasteur) (p. 356) ; (2) 

 Jennerian vaccination against smallpox (p. 603) ; (3) Anti- 

 cholera inoculation (Haffkine) (p. 472) ; (4) Anti-plague 

 inoculation (Haffkine) (p. 499) ; (5) Anti-typhoid inoculation 

 (Wright and Semple) (p. 387) ; (6) Pasteur's method of inocula- 

 tion against hydrophobia, which involves essentially the same 

 principles (p. 618). 



Vaccines as a Method of Treatment. Within recent years the 

 principles of active immunity have been directly applied in the 

 treatment of already existing disease. This is largely due to the 

 work of Wright, who, from his study of the part played by 

 phagocytosis in the successful combat of bacteria by the tissues, 

 was led to advocate the treatment of bacterial infections by 

 carrying on an active immunisation against the causal agents 

 by the injection of dead cultures of the latter. The justification 

 for such a procedure lies in his contention that in many cases 

 infections are to be looked on as practically localised, e.g., the 

 cases of an acne pustule, or a boil. The view is that while 

 the local capacities of resistance may have been lowered, resisting 

 mechanisms in other parts of the body have not been brought 

 into play. The vaccine may thus stimulate these, and the focus 

 of bacterial growth may be flooded with antibacterial bodies. 

 (With regard to the details of the preparation of the vaccines, see 

 p. 134; the general principles supposed to underlie their use have 

 been discussed in connection with tuberculosis, p. 299.) Vaccines 

 have been used extensively in the treatment of acne, boils, 

 sycosis, tuberculosis, infections of the genito- urinary tract by the 

 b. coli, infections of joints by the gonococcus, and in many cases 

 considerable success has followed the treatment. Favourable 

 results have also been recorded in the case of more general 

 infections, such as ulcerative endocarditis, septicaemia, typhoid 

 fever, etc. In such cases it is stated that the best results are 



