418 THE PROCEEDINGS OP THE LTNNEAN SOCIETY 



Cholera will in like manner sometimes spread themselves 

 rapidly in certain spots subject to certain influences, but they ai'e 

 generally admitted not to be directly infectious. I think it may 

 fairly be deduced from these peculiarities that the plants to 

 which these diseases owe their origin, pass through different 

 stages of existence much in the same way as animal parasites have 

 been found to do. 



There is nothing improbable or contrary to what we know of 

 Nature in this hypothesis. The lowest forms of animal and 

 vegetable life approach one another so closely that there are 

 whole families which have been classed by eminent naturalists 

 sometimes in the one kingdom and sometimes in the other. 



It is easy also to imagine that a fungus which would germinate 

 freely in its proper " pabulum," and send out its fertile spores in 

 myriads throughout surrounding space, might be incapable of per- 

 fection and reproduction when conveyed to the body of a human 

 being, though quite capable of producing violent disease. And 

 accepting this as, I think, a probable solution of the question, we 

 would naturally be led to infer that diseases directly infectious, 

 which are supposed to have a somewhat similar origin, such as 

 Measles, Scarlet Fever, and Small-pox, are caused by vegetable 

 growths, which attain perfection and have the power of reproduc- 

 tion in the human body. 



At all events, it must be admitted that by studying and fol- 

 lowing out the life history of these parasitic plants, we shall be in 

 a better position than we now are to confer an immense benefit on 

 mankind by limiting the range of these diseases, if they cannot be 

 altogether extirpated. 



There is an immense field open here for investigation, and I 

 am most desirous that this very important branch of Biological 

 Science should receive the attention it merits from the members 

 of this Society. And I would recommend this line of inquiry 

 more particularly to those members who belong to the noble pro- 

 fession of medicine, as by the nature of their education and their 



