IMMUNITY IN TUBERCULOSIS 239 



body the immunizing organisms behave differently from those in arti- 

 ficial cultivations. This difference in behavior could be accounted for 

 on the supposition that under conditions of parasitic life, surrounded 

 as the bacilli are with complex fluids and more complex cells, they 

 form, in their growth, products which either are distinct from those 

 which are formed by them in cultures, or these products, in statu nas- 

 cendi, are acted upon and modified by the active and labile ferments 

 in the fluid and protoplasm of cells, with which the growth-products 

 must come into immediate contact. Professor Welch, to whom this 

 variation in behavior of bacteria under parasitic and saprophytic states 

 of existence was fully apparent, endeavored a few years ago in his 

 Huxley lecture to explain the difference in activity of bacteria growing 

 within and outside the body by supposing that in the body they are 

 induced to secrete substances the stimulus to the production of which 

 is absent in the culture tube. However this may be, it is evident that the 

 only form of immunity in tuberculosis which deserves the name has 

 been obtained by the employment for inoculation of living cultures 

 of the tubercle bacillus. 



Although the earliest experiments which had for their object the 

 production of immunity in small animals by means of previous inocula- 

 tion of products of the growth and of attenuated cultures of the tubercle 

 bacillus were published in 1890 (Martin and Grancher, Courmont and 

 Dor), yet, I think, the first really promising, because successful, achieve- 

 ments of this end were made by Trudeau in 1902 and 1903 and by 

 de Schweinitz in 1904. 



Trudeau protected rabbits from virulent tubercle bacilli by first 

 injecting them with a culture of bird tubercle bacilli, the subsequent 

 injection of virulent mammalian bacilli being made into the anterior 

 chamber of the eye. The rabbits to be protected were twice injected 

 subcutaneously at intervals of 21 days with cultures of the avian bacilli. 

 About one in four of the rabbits died within three months, profoundly 

 emaciated, but without tubercular lesions. The remaining animals 

 recovered and were apparently in good health, when, with an equal 

 number of controls, they were inoculated in the eye with a culture of 

 mammalian tubercle bacilli. The results are instructive: In the con- 

 trols little or no irritation following the operation is observed and the 

 eye remains quiescent or nearly so for about two weeks, when the 

 changes described in the early parts of this address manifest them- 

 selves. After a few weeks general inflammation of the structures of 

 the eye develops, the inoculation wound becomes cheesy and the eye is 

 more or less completely destroyed. The disease, however, remains 

 usually localized in the eye for many months, and may remain there 

 permanently, depending upon the virulence and number of bacilli 

 injected. 



