STUDIES OF 1868, 1809, 1870 185 



atrophied because it has become useless) the still recog- 

 nizable forms of organisms which were present in the 

 stomach of the worm, especially of those organisms 

 which have been so Httle active as to permit the worm 

 to continue its development in spite of the weakening 

 which they have caused. Among these is a small fer- 

 ment in chains, analogous to the organism figured in the 

 fourth section of Fig. 8, page 70. When one finds this 

 in the stomach of a chrysalis or of a moth he may 

 rest assured that the disease of the jnorts-flats was 

 present at the end of the metamorphosis, and that the 

 egg is suspicious. We may tiy to find in this direc- 

 tion a criterion of purity which the egg itself is in- 

 capable of furnishing, since the egg contains nothing. 

 The heredity which is transmitted is not the inheritance 

 of a germ; it is the inheritance of a function, a reversed 

 vaccination, favoring the invasion of the common germ 

 of the malady, as ordinary vaccination prevents the 

 invasion of the specific germ. Such is, we might say 

 to-day, the inheritance of tuberculosis. If the tubercle 

 organism is not common, if it is incapable of developing 

 outside of the body, a fact of which we are not yet very 

 certain, it is at least widely di'^tributed, and has no 

 need, as we see in case of flacherie, of being transmitted 

 through the parents by heredity in order to attack the 

 offspring. All that is necessary is a hereditary feebleness 

 in the functioning of the lungs. The soil prepared, the 

 seed always ready, the disease will always find the 

 occasion to implant itself. 



On the contrary, as in flacherie, there will be always 

 some hereditary predispositions which will be effaced 

 owing to favorable conditions. 



In conclusion, at the end of his Etudes, Pasteur found 

 not only that he had solved the problem which he had 

 undertaken on the regeneration of sericiculture, but 



