8 



for certain phenomena, the causes of 

 which have not been fully developed. In 

 applying these terms to medical and 

 physiological subjects, I may be allowed 

 to define what I think they designate, and 

 what I intend to convey by them. By 

 the word theory I mean a rational ex- 

 planation of the cause or connexion of 

 an apparently full or sufficient series of 

 facts: by hypothesis, a rational conjec- 

 ture concerning subjects in which the 

 series of facts is obviously incomplete. 



The formation of an hypothesis ex- 

 cites us to enquiries, which may either 

 confirm or confute our conjectures ; and 

 which may, by enabling us to discover the 

 deficient facts, convert our hypothesis into 

 a theory. Believing the facts collected by 

 the ingenuity and industry of Mr. Hunter, to 

 be sufficient to establish his opinions respect- 

 ing life, I have therefore called them, a theory. 



