290 TUBEKCULOSIS 



again grouDd up in distilled water, centrifugalised, and the clear fluid set 

 aside ; the process is again and again repeated with the residue until, 

 on centrifuging, none is left. The successive supernatant fluids are 

 mixed and concentrated, and constitute the tuberculin. As this fluid 

 gives a cloudiness with glycerin, Koch considered it contained the 

 glycerin -insoluble constituents of the "old tuberculin." 



(4) Koch's New Tuberculin {Bazillenemulsion). — A bacillary mass 

 is dried and ground in 50 per cent, glycerin in water till a clear fluid 

 results. This tuberculin is thus equivalent to a mixture of tuberculin-0 

 and tuberculin-E. 



(5) Tuberculin Biraneck. — This preparation is an extract of tubercle 

 bacilli with 1 per cent, phosphoric acid, the effect of which is supposed 

 to be to destroy some of the more harmful constituents. 



A number of other tuberculin preparations have been used, but the 

 above are the most important. 



The original tuberculin was introduced by Koch for the 

 treatment of local tuberculous infections. The supposed 

 rationale was that when the artificially produced toxins were 

 injected into the body their action, added to that of the bacilli 

 growing in the focus of infection, caused a sudden exacerbation 

 of the necrotic effect occurring around the bacilli, which resulted 

 in ulceration, whereby the living bacilli were thrown off. It 

 has been found that the injection of the tuberculin directly 

 into the tubercular focus is often not followed by a tuberculin 

 reaction, and although there are other factors to be taken into 

 account this militates against the view that a local concentration 

 of toxin is a sufficient explanation of the phenomenon. The 

 tuberculins are now used for the purposes of diagnosis and to 

 originate immunisation. Their action is extremely complicated 

 and not yet clearly understood, and may be considered under the 

 headings of the production of supersensitiveness, and immunity 

 phenomena. 



(1) Phenomena of Supersensitiveness. — (a) The Original 

 Tuberculin Reaction. — This can be manifested with any of the 

 tuberculin preparations. Thus, if -25 c.c. of " old " tuberculin 

 be hypodermically injected into a healthy individual, there occur 

 in three or four hours malaise, tendency to cough, laboured 

 breathing and moderate pyrexia, all passing off in about twenty- 

 four hours. If, however, only 0-01 c.c. be injected into a tuber- 

 cular subject, similar symptoms but in a much more aggravated 

 form (the so-called tuberculin reaction) arise, and if there be 

 present a local tubercular focus— e.#., lupus — there occurs round 

 it a definite inflammatory reaction with, it may be, ulceration. 

 Similar phenomena of " supersensitiveness " are produced by the 

 injection of almost any foreign proteid into an animal. The 

 subject will be discussed in the chapter on Immunity under the 



