254 TUBERCULOSIS. 



dog against bacilli derived from man. But these are not 

 yet conclusive. Further, many attempts have been made 

 at immunisation against the tubercle bacillus by the employ- 

 ment of its toxic products. The most successful have been 

 those of Maragliano. We have seen that this author dis- 

 tinguishes between the toxic bodies contained in the bodies 

 of the bacilli (which withstand, unchanged, a temperature 

 of 100 C.) and those secreted into the culture fluid (which 

 are destroyed by heat). The substance used by him for 

 immunising his animals consists of three parts of the former 

 and one of the latter. Commencing with 2 mgrms. of the 

 mixture he increases the dose by i mgrm. daily, till a dose 

 of 40 to 50 mgrms. is reached. This latter quantity is in- 

 jected daily for six months, by which time a high degree 

 of immunity has been reached. The animals employed are 

 the dog, the ass, the horse. The serum obtained from 

 these is capable of protecting healthy animals against an 

 otherwise fatal dose of tuberculin. Maragliano does not 

 appear to have studied the effects of this serum on tuber- 

 cular animals, but it has been tried in a great number of 

 cases of human tuberculosis, 2 c.c. being injected sub- 

 cutaneously every two days. Improvement is said to have 

 taken place in a certain proportion, especially of mild non- 

 febrile cases. 



Active Immunisation by Intracellular Toxines. Koch 

 in 1897 published the results of further researches on 

 tuberculosis. These consisted ( i ) of an attempt to immunise 

 animals against the tubercle bacillus by employing its 

 intracellular toxines ; (2) of trying to utilise such an im- 

 munisation to aid the tissues of an animal already attacked 

 with tubercle the better to combat the effects of the bacilli. 

 To obtain the intracellular toxines is difficult, as they appear 

 to be intimately connected in the protoplasm with several 

 very insoluble fatty acids. The method was as follows. 

 Bacilli from young virulent cultures were dried in vacuo, 

 and then well rubbed up with an agate pestle and mortar, 

 treated with distilled water and centrifugalised. The clear 

 fluid was decanted, and is called by Koch " tuberculin O." 



