TUBERCULOSIS. 231 



individual, so that, a short time after its enthusiastic 

 reception as a "gift of the gods," tuberculin was placed 

 upon its proper footing as a diagnostic agent valuable in 

 veterinary practice, but dangerous in human medicine, 

 except in cases of lupus and other external forms of the 

 disease where the destroyed tissue could be discharged 

 from the surface of the body. 



The method of preparation of tuberculin is rather 

 simple. Small flasks exposing a considerable surface of 

 liquid are filled with about 25 c.cm. of bouillon contain- 

 ing about 4 per cent, of glycerin. The bouillon is prefer- 

 ably made with calf- instead of ox-meat. When thor- 

 oughly sterile the surfaces are inoculated with pure 

 cultures of the tubercle bacillus and are stood in an 

 incubator. In the course of two weeks a slight surface 

 growth is apparent, which in the course of time develops 

 into a pretty firm pellicle and gradually subsides. At the 

 end of four or six weeks development ceases and the 

 pellicle sinks. The contents of a number of flasks are 

 then collected in an appropriate vessel and evaporated 

 over a water-bath to one- tenth their volume, then filtered 

 through a Pasteur-Chamberland filter. This is crude 

 tuberculin. 



When such a product is injected in doses of a fraction 

 of a cubic centimeter an inflammatory and febrile reac- 

 tion occurs. The inflammation sometimes causes super- 

 ficial tuberculous lesions (lupus) to ulcerate and slough 

 away, and for this reason is of some value in therapeutics, 

 although attended with the dangers mentioned above. 

 The fever is sufficiently characteristic to be of diagnostic 

 value, though the tuberculin can only be used as a diag- 

 nostic agent in practice upon animals. 



A recent important work upon tuberculin has been 

 done by Koch. 1 



In his experience the attempts made to produce im- 

 munity to the tubercle bacillus by the injection into 

 animals of attenuated cultures proved failures, because 



1 Deutsche met?. Wochenschrift, 1897, No. 14. 



