OF DISEASE GERMS. 259 



It is from researches in this direction that we may 

 hope to gain knowledge which may lead to the dis- 

 covery of means of destroying the contagious germinal 

 matter while in the blood, and of preventing the 

 influence of poisons of another kind upon the living 

 bioplasm of the blood, capillary vessels, and of that of 

 the tissues immediately adjacent. 



A careful study of the course and symptoms of the 

 various fevers which have been prevalent at different 

 periods, leads to the suggestion of the probability that 

 from time to time new germs are produced, and 

 that old ones deteriorate and disappear. The new 

 forms may be closely allied to already existing 

 forms, and to forms which have existed previously, 

 but nevertheless the results occasioned by their 

 development are so peculiar that we cannot but sup- 

 pose they are occasioned by a poison of a special kind. 

 It is even possible to discern differences between cases 

 of the same type of contagious fever, which would be 

 sufficient to justify us in arranging them as species of 

 a genus, or as varieties of a species. 



It is not probable that disease germs have sprung 

 from insects or animalcules, or any kind of vegetable 

 organism, neither have they originated in the external 

 world, and seized upon man, but they have been 

 derived by direct descent from the normal living 

 bioplasm of the organism. They have originated in 

 man, and if man is not indeed responsible for their 

 origin, he has certainly himself imposed the conditions 



