16 CLINICAL DIAGNOSTICS. 



eases with which he must come in contact, will never become 

 a good diagnostician. 



Diagnosis per se has a different value depending upon 

 whether it is made for a scientific or wholly practical purpose. 

 It is often symptomatic and thus merely cloaks our ignor- 

 ance ; diabetes insipidus, colic, for instance. The purpose of 

 diagnosis is more nearly attained when it includes the cause of 

 the disease ("etiological diagnosis"), which is of value even if 

 we do not know more of the cause than that it is some specific 

 infection (influenza). An anatomical diagnosis is not 

 conclusive because it does not indicate the cause (nasal catarrh, 

 bowel catarrh). An ideal diagnosis would be "etiologico- 

 anatomical'' (skin glanders, acarus mange, verminous bron- 

 chitis). A correct prognosis and rational treatment are largely 

 dependent upon a knowledge of the cause and morbid changes 

 of the disease. 



It is not enough to diagnose a nodular, itching and spread- 

 ing eruption of the skin, we must also determine the cause or 

 our prognosis and treatment cannot be correct and rational. 

 Such eruptions are due to various causes and an exact knowl- 

 edge of them is an important item. The same may be said of 

 affections of internal organs. 



A final diagnosis is made either by considering the deter- 

 mined symptoms directly {direct diagnosis) or by a process of 

 exclusion, i. e., we review in our mind all the diseases in which 

 the symptoms determined occur, or in which some of these 

 symptoms occur, and then we exclude those diseases in the 

 course of which, if present, we usually observe additional 

 symptoms {differential diagnosis). 



The difficulties encountered in diagnosing internal dis- 

 eases vary considerably ; in some cases a good anamnesis suf- 

 fices as a basis for making a definite diagnosis: epilepsy, par- 

 turient paresis. In other cases the experienced practitioner 

 requires but a glance at the patient : tetanus. The rule, how- 

 ever, is never to make a diagnosis until a thorough and careful 



