CLASSIFICATION OF DISEASES. 127 



nearly the standard of a pathological nosology ; was further 

 developed by Bichat, and adopted by Dr. Craigie in 1836. 



The results of modern investigations into disease prove that 

 many ailments hitherto supposed to be merely functional are in 

 reality accompanied by organic alteration of tissue ; and it is not 

 unreasonable to suppose that many of the so-called functional 

 diseases will be found to depend upon an alteration of structure, 

 and even where no organic change can be detected in cases 

 where tlie existence of disease cannot be doubted, we may 

 attribute our failure to the imperfection of our means and in- 

 struments of investigation, or our modes of using them. 



Dr. Aitken, to whose works the reader is referred for further 

 information, observes that " a perfectly philosophical or natural 

 system of classification aims at having the details of its plan to 

 agree in every respect with all the facts as they exist in nature, 

 and to be, as it were, a ' translation of the thoughts of tlie 

 Creator into the language of man.' To effect this end, arrange- 

 ments, as they naturally exist, require to be traced out, not 

 devised. The tracks in which such a pursuit must be followed 

 up, and in which our knowledge is as yet deficient, may be 

 shortly indicated under the following heads, namely : — 



" (l.j The affinities or alliances of diseases with each other. 

 (2.) The morbid anatomy of diseased parts. (3.) The com- 

 munication, propagation, inoculation, generation, development, 

 cause, and spontaneous natural termination of diseases. (4.) The 

 connection of the phenomena recognised during life with the 

 facts of morbid anatomy. (5.) The geographical distribution of 

 diseases. (6.) The succession of diseases, as far as they can 

 be traced through past ages ; the peculiarities they have ex- 

 hibited at different periods in the world's history, or within 

 comparatively recent cycles of years. 



" But the time has not yet come for a classification on a 

 basis so comprehensive, simply because tlie material does not 

 exist; and attempts to make so-called natural systems of 

 arrangement must end in disappointment, on account of the 

 uncertain and fluctuating data on which they must be based." 



The arrangement of animal diseases, and their division into 

 classes, groups, and orders, is a very difficult matter. They 

 might certainly be arranged according to their pathology, to 

 their causes, to the tissue or the systems of the animal body 



