PROBLEMS OF INTERNAL MEDICINE 213 



material for the rising edifice of a rational, exact diagnosis. The 

 sphygmograph, the thermometer, the ophthalmoscope, the laryngo- 

 scope, the binaural stethoscope, the stomach tube, the various 

 means for studying the blood-pressure, all have brought their aid, 

 while but yesterday the discovery of Roentgen has given us new 

 and unhoped for diagnostic assistance. 



At the same time physiological chemistry which, with the work 

 of Berzelius on the urine, had taken its place by the side of the 

 more purely physical methods of investigation, has year by year 

 given us greater diagnostic assistance in the analysis of the different 

 secretions and excretions of the body and in the explanation of 

 the various metabolic processes of the economy. 



The development in the hands of Duchenne and Erb and Remak 

 of electrical diagnosis, together with the great advances in physio- 

 logy and pathology of the nervous system, has afforded explanation 

 for much that was previously incomprehensible and has given us 

 powers of diagnosis which a few generations ago would have seemed 

 almost magical. 



Finally Pasteur and Koch, with the introduction of bacteriolog- 

 ical investigation, opened the way to the discovery of the causal 

 agents of a large group of infectious diseases. These discoveries, 

 followed rapidly by the evolution of methods allowing of the clin- 

 ical demonstration of many pathogenic microorganisms, afforded 

 an early, exact, and positive diagnosis, on the one hand in conditions 

 where previously the disease was recognizable only at a stage in 

 which it had made inroads into the system so great as to be often 

 beyond relief, as in tuberculosis, and on the other, in maladies, 

 the existence of which without these methods was to be definitely 

 determined only after the onset of an epidemic, as in cholera, 

 plague, and influenza. When one thinks of what the last quarter 

 of a century has taught us with regard to tuberculosis, anthrax, 

 tetanus, diphtheria, typhoid fever, cholera, plague, dysentery, 

 influenza, not to speak of the great group of wound-infections, we 

 may begin to realize what bacteriological methods have done for 

 diagnosis how many diseases have been cleared up how many 

 symptoms have been explained. 



In like manner Laveran, with the discovery of the parasite of 

 malarial fever, did much to bring certainty and precision into a 

 field in which many had gone astray, while opening the way for 

 the important observations of Theobald Smith and all the know- 

 ledge which we have gained in recent years with regard to the 

 hematozoa of man and animals. 



As a direct result of the introduction of bacteriological methods, 

 the study of the manner of action of infectious agents and their 

 toxic products upon the animal organism, as well as of the powers 



