LUETIN REACTION 643 



to the extract of pallida. Theoretically, one should not expect to 

 obtain an allergic reaction in syphilis so long as the activity of pallida 

 is maintained at its maximum, or in the very early stages, before there 

 is sufficient time for antibody formation. One can reasonably expect 

 the appearance of the phenomenon when the activity of the micropara- 

 site begins to abate through a gradually acquired defensive power of 

 the host, or under an effective therapeusis, as in the later stages of the 

 disease and in hereditary syphilis. Practical results have borne out 

 these theoretic expectations. 



Preparation of Luetin. At least six different strains of pallida in pure cul- 

 ture are being used by Noguchi in the preparation of lueiin. These are cultivated 

 in ascites-kidney agar for periods of six, twelve, twenty-four, and fifty days, at 37 

 C., under anaerobic conditions. The tubes showing large numbers of spirochetes are 

 then selected, the oil is poured off, the tube is cut, the agar column is removed, and 

 the tissue then cut off. The ascites-agar cultures are then carefully ground in a 

 sterile mortar, the resulting thick paste being gradually diluted with a fluid culture 

 until a homogeneous liquid emulsion is secured. The preparation is next heated 

 for an hour in a water-bath at 60 C., and then tricresol or phenol added to make 0.5 

 per cent. Cultures are made from this suspension, and rabbits inoculated intra- 

 testicularly ; both, after suitable intervals, must show an absolutely sterile preparation. 



The luetin should be kept in the refrigerator when not in use. The 

 isolation of Treponema pallidum in pure culture is a difficult procedure, 

 and, obviously, a luetin must be prepared of pure cultures and from as 

 many different strains as possible. While pallida quickly loses its patho- 

 genicity in artificial culture-media and is also highly susceptible to the 

 influence of germicides, its preparation, nevertheless, is an important 

 matter requiring skilful supervision. 



A control fluid prepared of sterile agar and bouillon in exactly the 

 same manner as luetin, was originally advised by Noguchi, but recently 

 he claims that its use is not necessary. 



Method of Application. Luetin is not applied to an abrasion of the 

 skin, but is injected intracutaneously with a very fine needle and a sterile 

 syringe. According to directions from the Rockefeller Institute, the 

 luetin is to be well shaken, diluted with an equal part of sterile salt 

 solution, and 0.07 c.c. injected (0.035 c.c. undiluted). A slightly 

 smaller dose, as, e. g., 0.05 c.c., may be used for children. The skin of 

 the upper arm is usually selected as the site for inoculation. If a 

 control fluid is used, the luetin may be injected into the skin of the left 

 and the control fluid into the skin of the right arm, or both injections 

 may be given in the same arm, about two inches apart, the control 

 being above the luetin. As shown by Sherrick, 1 and confirmed by my 

 1 Jour. Amer. Med. Assoc., 1915, July 31, 404. 



