DEVELOPMENT OF THE GERM THEORY. 25 



proved that this disease was of two kinds, both depending upon 

 micro-organisms. In his investigations, he came upon some very 

 interesting points as to the mode of infection, which threw much 

 hght upon all diseases, whether affecting animals or human beings. 

 First, that in the eggs laid by a diseased moth the germs could 

 maintain their vitality when thus enveloped and protected from 

 the outer air, and so could transmit the disease by heredity. 

 Secondly, that climbing over each other, after having crawled over 

 infected leaves, they would inflict occasional pricks with the sharp 

 hooks on their legs, thus causing direct inoculation of the disease; 

 and thirdly, that in a perfectly healthy state the digestive functions 

 of silkworms were so active that the germs of the disease were 

 carried away quickly or destroyed in the same manner as the 

 leaves in the process of digestion ; but that if by any cause the 

 digestion of the worms be impaired, the germs were able to mul- 

 tiply rapidly, and the worm was doomed to perish. 



By destroying the infected eggs and the worms suffering from 

 hereditary weak digestion, and by improving the hygienic condi- 

 tions of the environment, he was able completely to stanip out the 

 disease, and to restore the silkworm industry to its former 

 prosperity. 



Lemaire, proceeding upon Pasteur's lines, after proving that 

 the presence of carbolic acid was inimical to the life of higher 

 plants and animals, carried his researches further, and found that 

 the lower organisms were similarly affected by the same material; 

 and that the addition of a small quantity of carbolic acid to fluids 

 in which putrefaction and fermentation would ordinarily take 

 place prevented the incidence of these processes ; and reasoning 

 that disease processes, such as pus formation, w^ere the result of 

 fermentations or decompositions brought about by the action of 

 germs, he concluded that they might be prevented by similar 

 treatment, and he actually applied this antiseptic treatment suc- 

 cessfully on the wounds of the human subject and of the dog. 



Lister independently came to the same conclusions ; but owing 

 to the difficulty of killing the germs after they had once made 

 their way into the tissues, he recognised the absolute necessity of 

 preventing such organisms gaining access to the wounds at all, and 

 founded his well-known antiseptic treatment for the attainment of 

 this end. 



