344 INFECTION AND IMMUNITY 



From this stock emulsion small quantities may be drawn off and 

 diluted for therapeutic use. 



The initial dose given by Wright in staphylococcus infections, 

 in which the method has been most frequently employed, varies 

 from fifty to one hundred millions of bacteria. In working with 

 the tubercle bacillus, the ordinary tuberculin dosage is adhered to. 



Wright, in his work, makes use of the opsonic index in order to 

 estimate changes in the resistance of the patient against the given 

 infection. In other words, he bases his judgment as to whether the 

 patient is improving or not, upon the opsonic power of the patient's 

 serum. In following the opsonic index of a patient during systematic 

 treatment with vaccine, Wright has found definite changes upon 

 the basis of which he constructs a curve of opsonic power. Imme- 

 diately after the injection of vaccine, he finds that there is a brief 

 period during which the opsonic power of the patient is depressed 

 below its original state. This he calls the negative phase. The 

 length of time occupied by this negative phase depends both upon 

 the condition of the patient and upon the size of the dose given. 

 It is usually completed within twenty-four hours. After this, there 

 is a gradual rise in the opsonic power, at first rapid, later more 

 slow, until a maximum is reached after a varying number of days. 

 This period of rise represents the positive phase. The second inocula- 

 tion with. vaccine should, according to Wright, be made when the 

 opsonic power is again beginning to sink after the highest point of 

 the positive phase. 



The facts of Wright's investigations have been given in the 

 preceding without much critical consideration. Those features which 

 concern themselves with the proof of the opsonic properties of 

 normal and immune serum have been of the greatest scientific 

 importance and a great deal of benefit has accrued from the renewed 

 attention turned by him toward methods of active immunization in 

 human beings. Vaccine therapy in many conditions has come to 

 stay, although some of the very extravagant earlier claims have had 

 to fall down. It is also pretty certain at present that the opsonic 

 index measurements as a guide to treatment are of very little value 

 and may even mislead. Prophylactic vaccination in various diseases 

 is dealt with in the chapters on the individual infections. 



Leucocytic Substances. In the sections upon Phagocytosis and 

 Opsonins, we have discussed the protective action exerted by the 

 living leucocytes against bacterial infection and the relation of these 



