008 PATHOGENIC MICROORGANISMS 



patients this process is followed by a sharp conjunctival congestion 

 lasting from one to several days. 



The preparation used for this purpose is produced in the following 

 way: 



"Old Tuberculin" is treated with double its volume of 95 percent 

 alcohol, the precipitate allowed to settle and the alcohol then filtered 

 off through paper. The sediment is washed with 70 per cent alcohol 

 until the filtrate runs clear, then pressed between layers of filter 

 paper to remove excess of moisture, scraped into a dish, dried in 

 vacuo over H^SCU, and broken up in a mortar under a hood. 



Solutions of the powder are made in sterile normal salt solution, 1 

 per cent by weight, boiled and filtered. The solutions are used in 

 strengths of 0.5 to 1 per cent, a drop of which is instilled into the con- 

 junctival sac. 58 



Cutaneous Tuberculin Reaction. Von Pirquet 59 has suggested the 

 cutaneous use of tuberculin for diagnostic purposes. A 25 per cent 

 solution of "Old Tuberculin" was first used. At present the undi- 

 luted substance is employed. 



After sterilization of the patient's forearm, two drops of this solu- 

 tion are placed upon the skin about 6 cm. apart. Within each of these 

 drops scarification is done, and the skin between them scarificed as a 

 control. Within twenty-four to forty-eight hours, in tuberculous 

 patients, erythema, small papules, and herpetiform vesicles will appear. 

 According to recent investigations, about 70 per cent of adults show a 

 positive reaction. This diminishes its diagnostic value for adults. 



Moro 60 has modified this by making a 50 per cent ointment of 

 tuberculin in lanolin and rubbing it into the skin without scarification. 



Complement Fixation in Tuberculosis. 61 The problem of comple- 

 ment fixation for diagnostic purposes in tuberculosis has been very 

 actively investigated of recent years. The most promising results have 

 been reported with an antigen made by Besredka of a filtrate of an 

 egg-meat-broth, upon which the tubercle bacilli had been grown for 

 several weeks with a similar filtrate of cultures on a watery extract of 

 potato with glycerin, used by Petroff, and with an antigen made by 

 Miller and Zinsser by triturating dead tubercle bacilli with dry crystals 



58 The conjunctival test is not in general use at the present time owing to pos- 

 sible dangers to the eyes. 



m -v. Pirquet, Berl. Win. Woch., xx, 1907; Med. Klinik, xl, 1907. 



69 Moro, Munch, med. Woch., 1906, p. 216. 



61 H. E. Miller, Jour. Lab. & Clin. Med., 1916, i, 816. 



