VEGETABLE ORGANISMS. 77 



to depend upon the growth and development of 

 vegetable organisms, are local affections confined to a 

 part of the body not involving the blood, while for 

 the most part, the different forms of contagious fevers 

 are general affections in which the whole mass of the 

 blood, and, in some cases, every part of the body, is 

 affected, and is capable of communicating the disease. 

 In fungus diseases, the structure of the vegetable 

 organism can be made out without difficulty, and the 

 vegetable examined in every stage of its development. 

 The microscopic characters are distinct and definite 

 enough. No such success attends our efforts to prove 

 that vegetable organisms are truly the active agents 

 in contagious fevers. And in many of the diseases 

 which are at this time considered to be actually due 

 to the multiplication of vegetable germs, it is doubtful 

 if the tissues and organs invaded were perfectly 

 healthy at the time of invasion. For all persons ex- 

 posed are not attacked, and if not in all, at least in 

 the great majority of instances known, the view that 

 a morbid change must occur before the tissue is in a 

 state to be invaded by the fungus growth, is tenable. 

 In fact, it has been already shown that the fungi 

 which commonly grow on the surface, and in other 

 parts of the body, do not produce disease. The 

 germs of fungi may remain perfectly passive and 

 quiescent in healthy textures, growing and multi- 

 plying only in -those which have already deteriorated 

 in consequence of disease or old age* The growth of 



