434 Missouri Agricultural Report. 



device. Theory, practice, adjustment, these are the three stages. 

 For illustrative purposes, we may trace them in that improvement 

 which has been the result of successful warfare against infectious 

 diseases. Diptheria which once annually destroyed a large number 

 of young lives has been practically wiped from the earth. The 

 first stage in this beneficent change came with the development of 

 the theory that the disease was due to the inroads of certain bacteria 

 and to a poison which the bacteria made within the body by their 

 action upon the tissues. The second period saw the discovery of 

 an anti-toxin and the invention of a process for introducing it 

 into the human system. The third was a period of education and 

 adaptation. The date of this third period was so recent that there 

 are probably few present here who cannot look back to its earlier 

 years and bring to mind at least one young person who died, not 

 because the means of cure were unobtainable, but because the 

 physician in attendance had not accepted the newer theories of dis- 

 ease and applied them in his practice. He had not yet entered upon 

 that period of adjustment, which at this time is fortunately about 

 complete. The warfare against tuberculosis, on the other hand, 

 having passed successfully the first and second stages, has halted 

 at the entrance to the third. This delay is due to many causes. 

 One is the fact that the prevention of this particular disease is de- 

 pendent quite as much upon the enlightenment of a large body of 

 laymen as upon the training of a few physicians and health of- 

 ficers ; and the education of the laity is a slow process. Another is 

 the widely accepted belief that the disease is transmitted princi- 

 pally by inheritance, and that the pain and sorrow which it brings 

 are inevitable. A third is the fact that the progress of tuber- 

 culosis is without those spectacular and sensational features which 

 attend such maladies as diphtheria and smallpox. 



In the coming of those improvements which have for their 

 object the saving of time and energy and the increase of comfort 

 we may trace the same three eras. The possibility of aerial loco- 

 motion rests upon a well substantiated theory, but theories even 

 when well substantiated offer uncertain support to those who would 

 fly through the air, and for this reason we have not yet begun to 

 think of tearing up our railway tracks and of sending our locomo- 

 tives to the junk shop in preparation for adopting the newer 

 methods of travel. The consumption of smoke, on the other hand, 

 has passed the stage of practice as well as that of theory and at 

 present is prevented only by warring human interests from con- 

 ferring its inestimable benefits upon mankind. These interests 



