TUBERCULOSIS TUBERCULIN THERAPY 715 



suitable for practical use, since they are neither absorbed nor disposed of 

 in other ways, but remain a long time unaltered at the point of inocula- 

 tion and occasion smaller or larger abscess. " 



Koch showed further that while the injection of tuberculous guinea- 

 pigs with large doses of tubercle bacilli produced rapid death, frequently 

 repeated small doses exerted a favorable effect upon the site of infection 

 and the general condition of the animals. The same observer also 

 realized that the harmful effects of injections of dead tubercle bacilli 

 were due to the non-absorbable parts of the bacilli. He attempted to 

 extract the immunizing substances, and in this way produced his first 

 or Old Tuberculin. When injected into tuberculous guinea-pigs, old 

 tuberculin produced a rapid general reaction without any local necrosis 

 or sloughing, whereas when injected into a healthy guinea-pig, no re- 

 action, either local or general, was produced. The fact that the general 

 results produced by old tuberculin were analogous to those obtained by 

 his first vaccine, except that local necrosis did not occur, induced Koch, 

 in 1891, to promulgate it as a specific cure for tuberculosis in human 

 beings. 



It is hardly necessary to describe the hopeful anticipation with which 

 it was received, and the keen disappointment that followed its earlier 

 clinical use. .Indiscriminate use, extravagant expectations, and ex- 

 cessive dosage combined to yield results so discouraging as to swing the 

 pendulum of medical opinion so far the other way that even now the 

 very word " tuberculin " suggests to many minds failure, and something 

 to be avoided. 



A few earlier followers of Koch continued their studies in the endeavor 

 to discover the causes of failure in tuberculin therapy. Their researches 

 have led to new principles in treatment and to more exact knowledge of 

 its indications, as well as its contraindications. As now employed, its 

 use being restricted to suitable patients and administered in safe 

 graduated doses, and accepting as evidence only the statements of those 

 who have used tuberculin and not of those who believe it to be dangerous 

 and have never used it, one deduction is justified: that while tuberculin 

 is not a specific "cure" for tuberculosis, any more than hygiene, diet, 

 and climate are cures, it helps to arrest the disease and is in general 

 a useful factor in the treatment of certain types of the disease. Clinical 

 studies have shtfwn, however, that immunization of the tuberculous 

 patient is frequently a difficult procedure, owing to the fact that such 

 patients are prone to develop a remarkable state of hypersusceptibility, 



