294 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



twenty-four to forty-eight hours a dermatitis then develops which 

 is characterized by the appearance of miliary nodules of variable 

 size and number, which occur either singly or confluent. At the 

 same time there is a more or less extensive general redness of the 

 affected area, accompanied by a certain amount of itching (see 

 Plate IX). 



Regarding the clinical value of the method our knowledge is as 

 yet too meagre to warrant its general recommendation, v. Pirquet 

 states that he has been able to obtain positive results only in highly 

 susceptible individuals, but suggests that it may be tried, if for 

 any reason the cutaneous or the eye reaction cannot be employed. 



THE LUETIN REACTION 



While a number of different investigators had previously attempted 

 a skin reaction diagnosis in connection with syphilis, satisfactory 

 results could hardly be expected as long as the successful cultivation 

 of the corresponding spirochete in pure culture had not been accom- 

 plished. The solution of the latter problem we owe to the painstaking 

 work of Noguchi, and to the same investigator belongs the credit 

 of having first prepared an antigen with which a specific syphilitic 

 reaction may be obtained in a large percentage of infected individuals- 



Preparation of the Antigen. Pure placental ascites agar cultures 

 of the pallida are ground up in a mortar with placental ascites 

 bouillon cultures of the organism until a fairly thin emulsion is 

 obtained. This is sterilized for one hour at 60 C. and treated with 

 carbolic acid to the extent of 0.5 per cent. The resultant product 

 Noguchi has termed luetin. After being tested for its sterility it is 

 ready for use. A similar preparation is made from sterile culture 

 material and constitutes the control fluid. 



Injection of the Patient. The injections are made intracutaneously, 

 0.05 c.c. of both the luetin and the control fluid being used as a 

 dose. The right arm is chosen for the latter and the left for the 

 former. It is advisable, moreover, to inject each arm at two points, 

 about 5 cm. apart. 



Reactions. While in non-syphilitic individuals the effect of the 

 luetin and the control injection is identical and merely represents 

 a slight traumatic reaction which recedes within forty-eight hours 

 and leaves no induration, there may be a marked difference between 



