Toxic Products 743 



tated absorption, but the absorption of bacilli in this chem- 

 ically altered condition was not followed by immunity, prob- 

 ably because the chemic composition of tubercle toxin (or 

 whatever one may name the poisonous product of the 

 bacillus) was altered by the reagents. 



Tuberculin, with which Koch performed many experi- 

 ments, was found to produce immunity only against tuber- 

 culin, not against bacillary infection. 



Pursuing the idea of fragmenting the bacilli, or treating them chem- 

 ically to increase their solubility, Koch found that a 10 per cent, sodium 

 hydrate solution yielded an alkaline extract of the bacillus, which, when 

 injected into animals, produced effects similar to those following the 

 administration of tuberculin, except that they were more brief in dura- 

 tion and more constant in result ; but the disadvantage of abscess for- 

 mation following the injections remained. The fluid, when filtered, 

 possessed the properties of tuberculin. 



Mechanical fragmentation of bacilli had been employed by Klebs 

 in his studies of antiphthisin and tuber culocidin, and Koch now used it 

 with advantage. He pulverized living, virulent, but perfectly dry 

 bacilli in an agate mortar, in order to liberate the toxic substance from its 

 protecting envelop of fatty acid, triturating only very small quantities 

 of the bacteria at a time. 



Having thus reduced the bacilli to fragments, he removed them from 

 the mortar, placed them in distilled water, washed them, and collected 

 them by centrifugation, as a muddy residuum at the bottom of an opal- 

 escent, clear fluid. For convenience he named the clear fluid TO; the 

 sediment, TR. TO was found to contain tuberculin. In order to 

 separate the essential poison of the bacteria as perfectly as possible from 

 the irritating tuberculin, the TR fragments were again dried perfectly, 

 triturated once more, re-collected in fresh distilled water, and recen- 

 trifugated. After the second centrifugation microscopic examination 

 showed that the bacillary fragments had not yet been resolved into a 

 uniform mass, for when TO was subjected to staining with carbol-fuchsin 

 and methylene-blue it was found to exhibit a blue reaction, while in TR 

 a cloudy violet reaction was obtained. 



The addition of 50 per cent, of glycerin had no effect upon TO, but 

 caused a cloudy white deposit to be thrown down from TR. This last 

 reaction showed that TR contained fragments of the bacilli insoluble in 

 glycerin. 



In making the TR preparation Koch advises the use of a fresh, highly 

 virulent culture not too old. It must be perfectly dried in a vacuum 

 exsiccator, and the trituration, in order to be thorough, should not be 

 done upon more than 100 mg. of the bacilli at a time. A satisfactory 

 separation of the TR from TO is said to only occur when the perfectly 

 clear TO takes up at least 50 per cent, of the solid substance, as otherwise 

 the quantity of TO in the final preparation is so great as to produce un- 

 desirable reactions. 



The fluid is best preserved by the addition of 20 per cent, of glycerin, 

 which does not injure the TR and prevents its decomposition. 



The finished fluid contains 10 mg. of solid constituents to the cubic 

 centimeter, and before administration should be diluted with physiologic 

 salt solution (not solutions of carbolic acid). When administering the 

 remedy to man the injections are made with a hypodermic syringe into 

 the tissues of the back. The beginning dose is 7 7 mg., rapidly increased 

 to 20 mg., the injections being made daily. 



