328 THE TUBERCLE BACILLUS 



Calmette says that crude tuberculin should never be used for the ophthalmo- 

 reaction because the glycerin present in solution acts as an irritant. He 

 uses a recently made 1 per cent, solution of dried tuberculin (twice preci- 

 pitated with 95 per cent, alcohol) in distilled water. One drop of the tuber- 

 culin is instilled into one eye. Three to five hours later, in all tuberculous 

 persons, there is congestion of the inner end of the palpebral conjunctiva, 

 and more or less oedema and swelling of the caruncle which is covered 

 with a slight fibrinous exudate. Lachrymation occurs and there is a little 

 discomfort but no pain. The reaction reaches its maximum in 6-10 hours, 

 and after 18 hours in children and 24 hours in the adult the signs subside 

 and disappear. 



In persons not infected with tuberculosis instillation occasionally produces 

 a little redness but there is never lachrymation nor any fibrinous exudate. 



The advantage of the ophthalmo-reaction is, according to Calmette, that 

 it indicates the presence of active lesions only and as a means of diagnosis 

 is of more value than the cuti-reaction. A negative reaction is sufficient to 

 exclude a tuberculous infection except in tuberculous persons suffering from 

 cachexia who have lost the power of reacting. Persons who have recovered 

 from a tuberculous infection give a negative reaction. [Other observers 

 confirm Calmette, finding that] with rare exceptions (some cases of enteric 

 fever, for instance,) a positive reaction indicates an active tuberculous infection. 



[7. Percutaneous reaction. Moro rubs a lanolin ointment containing 50 per 

 cent, of Koch's old tuberculin into the skin of the chest or abdomen over an 

 area of about three square inches. From 1-2 days after the application 

 numerous small red papules appear on the anointed surface in tuberculous 

 individuals. The eruption is transitory and the reaction quite painless. 

 The results are very comparable with those given by von Pirquet's method.] 



C. Tuberculins TA, TO, and TR. 



Koch investigated a number of complex products derived in various ways 

 from cultures of the tubercle bacillus. These are known as tuberculin TA, 

 tuberculin TO, and tuberculin TR. 



1. Tuberculin TA (alkaline tuberculin). Tubercle bacilli separated by 

 filtration from a virulent culture are treated with a 10 per cent, solution of 

 soda and after 3 days' exposure at room temperature the bacilli are killed 

 and the liquid can be filtered through paper. After neutralization the filtrate 

 is clear, slightly yellowish and contains numerous dead bacilli. Inoculation 

 of the filtrate produces results similar to, but rather more persistent than, 

 ordinary tuberculin, and often leads to the formation of an abscess contain- 

 ing sterile pus. After filtering through a bougie TA gives results identical 

 with ordinary tuberculin. 



2. Tuberculin TO and tuberculin TR. Bacilli from a young, virulent culture 

 are dried in vacuo in the dark and then rubbed up in an agate mortar for 

 a long time. This is a dangerous proceeding and should be carried out with 

 the utmost care. The powder so obtained is mixed with distilled water and 

 the emulsion centrifuged for 40 or 45 minutes (4000 revolutions a minute). 

 Two layers are formed ; the upper (obere), fluid and opalescent and containing 

 no bacilli, is decanted off and forms tuberculin TO. 



The muddy lower layer is dried, rubbed up again, mixed with disti led 

 water and centrifuged. The residue from the centrifuging is treated in the 

 same way and the operation is repeated several times. Finally the liquids 

 poured off after each centrifuging are mixed together and form tuberculin TR 

 [Riickstand]. 



Tuberculin TO is very different from tuberculin TR. 





