6 . Introduction. 



rational method of treatment, is possible only to those who have 

 become versed in these basic branches of learning. Only unpre- 

 judiced observation of nature and careful scientific study based 

 upon anatomy and physiology, can give such insight. "To attempt 

 to guess by speculation what is hard to learn even by thorough 

 investigation has failed in this as in every other field of natural 

 philosophy." (Samuel.) "The enigmas of disease are far too 

 complex, the intermingling of forces in the higher forms of life 

 are far too involved, that thought alone should successfully recog- 

 nize such threads, not even to mention their absolute demonstra- 

 tion. The pages of general pathology are filled with the vanity of 

 such attempts." (Samuel.) 



Our knowledge of disease is primarily obtained from observa- 

 tion of the external appearances of diseased human beings and ani- 

 mals, from accumulation bi experience with the external manifesta- 

 tions of disease (clinical observation) . As long as autopsies were 

 not permitted upon the bodies of the dead, diseases received con- 

 sideration only from such external features ; and there existed only 

 a symptomatic classification of disease. It was customary to speak 

 of jaundice, dropsy, ardent fevers, nervous fever, etc.. as diseases, 

 and to endeavor to explain by clever theories and all sorts of base- 

 less ideas the origin of internal afifections, whose cause and location 

 were for the most part unknown. They were regarded as mysteri- 

 ous occurrences, for which evil spirits or the influence of the stars 

 on the lower world should be held responsible ; and knowledge of 

 pathology and the art of healing as well had to be groped for in 

 darkness. Nothing beyond those morbid conditions caused by 

 wounds, by gross external violence, or such affections of the skin or 

 mucous surfaces which were patent to the eye, was dealt with in a 

 less confused manner. 



In many lines the physicians of antiquity, who sought to deter- 

 mine the nature of disease by dissection of human and animal 

 cadavers, gained astonishing experience, practical skill and- an ac- 

 quaintance with the subjects, as is manifest from the clever experi- 

 ments and methodical investigations of these early thinkers. But 

 in the centuries of the Middle Ages, so barren of medical advance- 

 ment, even long after the founding of the universities (which oc- 

 casionally did succeed in making isolated discoveries of value in 

 connection with physiology) medical science became stationary and 

 fixed, hemmed in betw-een philosophical systems on the one hand 

 and all manner of outgrowths from a purely speculative and 



