OPSONINS AND OPSONIC INDEX 91 



sible to increase the opsonic powers of the blood of an individual suffering 

 from an infection, by vaccinating him with killed cultures of the organism 

 with which he was infected. 



The determination of the opsonic index is a long and tedious affair so that 

 in practice it is only used when it is necessary to estimate the value of the 

 vaccine treatment or to control dosage. Under ordinary circumstances 

 clinical phenomena will indicate the correctness of dosage and interval 

 but certain cases that fail to do well should be checked by opsonin indicators. 

 The value rises slowly and steadily with appropriate vaccine, dosage and 

 interval, falls with too large quantity, shows no change with inadequate 

 quantities. 



The Local Reactions or Tests. We have learned in the past few years 

 that the skin and mucous membranes will react more or less specifically to 

 the bacterial proteins. It is a form of allergic (see page 66). There have 

 been developed local tests for tuberculosis, syphilis, typhoid, glanders and 

 other diseases. The first two being the most important are considered below. 

 The others are of similar nature. 



Tuberculosis. If tuberculin of any form be rubbed into an abraded skin 

 area (Von Pirquet's cutaneous) or injected between the layers (Moro's'per- 

 cutaneous) of the skin a red maculopapule or even vesicle upon an inflamed 

 base will appear within twenty-four hours. There may be a mild general 

 reaction of fever and malaise. A positive reaction to such an installation 

 simply indicates the presence of a tuberculous lesion and that an allergic 

 fstate of the skin exists but does not show whether or not the lesion is active. 

 For this reason it is only of value in children since three-fourths of adults 

 are believed to have a healed lesion within them. Not only upon the skin 

 but upon the conjunctiva can this reaction be obtained. 



Syphilis. The poison of the Treponema pallidum is called luetin. It is 

 made by grinding up in salt solution a culture of the germ, heating the result- 

 ing mass to 6oC. for an hour and preserving it with phenol. If this be in- 

 stilled into an abraded skin area a maculopapule or nodular eruption occurs 

 in a syphilitic. This positive outcome, however, appears only in late cases, 

 those of tertiary stages and in treated cases. It therefore complements the 

 Wassermann reaction, being positive where this is apt to fail. 



Schick Test. It has been found by Schick and others that if Ko minimum 

 lethal dose of diphtheria toxin in .2 c.c. of saline be injected into the skin of 

 a person, a swollen, pink, tender area will appear in persons susceptible to 

 infection with Klebs-LofHer bacilli. If no such reaction occurs, the person 

 is not susceptible. This depends upon the fact that if anti-toxin be present 

 in the blood it will combine with the toxin and no reaction will appear, while 

 if no anti-toxin be present the toxin is free to exert its effect. It has been 



