NON-RECURRENCE OF DISEASES. 127 



less destructive ravages of their enemies, as is the human 

 body from the recurrence of violent diseases. 



This view may explain the gradual extinction, or unex- 

 pected reappearance of trees, shrubs and flowers. The 

 Prim, a New England hedge-bush, began to fail, according 

 to Webster, in 1775, and finally perished. In 1664, com- 

 menced the mildew in wheat, in New England, which long 

 rendered it impossible to cultivate that grain on the Atlantic 

 coast of three Eastern States. So have the Morillo cherry 

 tree, the Buttonwood tree, the Linden, and some others, 

 begun to decay, some in one way, some in another. The 

 peach tree is unhappily dying off in New Jersey, so that, 

 perhaps, in a few years, we may have to look exclusively 

 to the South for that delicious fruit. 



Of all the known vegetable productions, the fungi ap- 

 pear to have the greatest variety of abating and destroy- 

 ing conditions. They poison their own soil, they depend 

 for luxuriancy on nice contingencies, they are the food of 

 many insects, who eat them up spores and stems, whilst 

 they prey voraciously on one another, fungus being super- 

 imposed on fungus, in an almost indefinite series. 



Thus, then, may we not improbably account for the 

 occasional disappearance and reproduction of malarious 

 diseases in malarious situations. 



The obstruction to their own reproduction on the part 

 of fungous vegetables may be, I speak it with great hesita- 

 tion, the cause of the non-recurrence of certain violent 

 diseases, such as yellow fever; while it may analogically 

 explain the non-recurrence of diseases produced by con- 

 tagious germs, such as small-pox, measles, &c. 



May I be pardoned here for a short digression? Liebig 

 has attempted to elucidate this difficult point by a chemi- 

 cal explanation. He avers that each contagious disease 



