310 STATE BOARD OF AGRICULTURE. 



is lift' iroin daisies, aiul if we should sow Uiis to wlicat and secure a yood crop, we 

 would be better satisfied than ever that the failure of the wheat was due to the daisies. 

 Should Ihis last experiment be repeated hundreds of times with success, there would 

 be no doubt any lon^'er in our miiuls that tlie daisies bore a definite injurious relation 

 to the production of wheat. Any farmer will accejit this as sullicient proof in the 

 above work; now that the daisies be substituted by tubercle bacilli and the proof 

 extended, many farmers (I say many because I know this from actual experience) 

 doubt it. Koch, in his initial work, examined hundreds of cases of tuberculosis and 

 found tubeii'le bacilli in every case— this certainly corresponds to daisies in every jjonr 

 wheat field. Not satisfied with this, he isolated this plant, the tubercle bacillus, 

 just as you niijrht take a daisy and isolate it in a pot by itself and freed from all 

 other plants. Instead of using soil for growing it, he, Koch, used blood serum in 

 which there were no other ])lants, germs, growing. Having secured the plant, tubercle 

 bacillus, in |)ure culture, as you would the daisy in tlie jK)t, known to be unmolested 

 by any other plant, he introduces this single plant, tubercle bacillus, into the body 

 of a sound animal, such as a guinea pig, just as it is possible to introduce the daisy 

 into a wheat field which is free from this plant. The tubercle bacilli develop in the 

 body of the guinea pig quite rapidly and eventually kill the guinea pig; the daisy 

 develops quite rapidly in the wheat field and gradually kills the wheat. It is just as 

 easy to follow one as the other. The proof goes still farther, the tubercle bacilli oiily 

 are found in the body of the animal, and no other germs, and these bacilli can again be 

 used for inoculating another animal. Koch, besides finding the bacilli in hundreds of 

 cases of tuberculosis, inoculated hundreds of animals, mostly guinea pigs. 



Many individuals who depend u)ion their experience in reading articles on tuberculosis, 

 and who find comfort in nourishing their own logical deductions, without having ever 

 seen a tubercle bacillus or a piece of tuberculous tissue, make guinea-pig inoculation a 

 scapegoat. The farmer who has battered against experience all his life and has 

 become a successful farmer, smiles (to himself) when he sees his city friend, who has 

 scarcely seen a farm, buy one and endeavor to manage it. Before going on the farm 

 the city friend was very conversant about farm topics, but when the reality arose it 

 was quite difl'erent and a failure resulted. Such is the case with many everyday 

 newspaper writers on the subject of tuberculosis. Their rea^ding knowledge is very 

 good, but their experimental knowledge is very faulty. One of these prominent writers 

 goes so far as to say that experimenters draw most of their deductions or inductions, 

 as the case may be, from the inoculation of guinea pigs, and carry them over in their 

 application to man and animals. It may be said with truth, I think, that no one 

 knows better than the bacteriologist the exact relation existing between this animal 

 and man so far as experimentation goes, and it is also true that the bacteriologist 

 is more careful of his conclusions than the individual who would frame them for him. 

 Fortunately there are not many such writers, but they do much injury if allowed 

 freedom of action. 



When a guinea pig contracts tuberculosis from a certain source, such as milk and 

 flesh, the experimenter or bacteriologist does not say that the same material will 

 produce tuberculosis in man or animal. He would not dare make such a statement, 

 for so far as he is concerned he is not certain. He says such material is likely to 

 produce or may produce tuberculosis in man. Why this qualification? 



1. ]\lan cannot be made an experimental animal. 



2. The exact susceptibility of man to tuberculosis is unknown. 



3. The great susceptibility of the guinea pig to tuberculosis by inoculation is known. 



4. The contagiousness and infectiousness of tuberculosis in man are known. 



5. The factors which render some men more susceptible, apparently, than others, are 

 practically unknown. 



■G. The bacillus (tubercle) in man and guinea pig is identical. 

 (Some of these points will be considered later. — Author.) 



All of these thoughts pass through tlie mind of the bacteriologist and necessarily 

 make him conservative in his conclusions. It is i:sually the man who speaks for the 

 scientific man, who originates the sweeping statements. It has been established that 

 the tubercle bacillus can be carried over from man to guinea pig, but with what 

 facility it could be carried back from guinea pig to man is not settled. Consequently 

 it is impossible to carry results back and forth with a precision that is shown in 

 carrying results from animal to animal of the same species. It is a recognized truth 

 of bacteriology that a pathogenic germ may be carried through certain animals and 

 become inocuous to animals which were susceptible in a high degree, and on the other 

 hand it may be made intensely virulent to animals which were wholly immune to the 



