MICROSCOPY, Clinical, the use of the microscope in the diagnosis of disease. The microscope, ever since its first construction, has been used in the study of disease processes, but only within comparatively recent years has it attained its present importance as an adjunct in the clinical diagnosis of many different types of disease. Owing to the development of knowledge of parasitic and infectious diseases, the physician of to-day is better able to make an accurate diagnosis by means of the micro scope than were his forefathers. The micro scope may be used not only to confirm a diag nosis which has been made by ordinary clinical methods, but it may abbreviate such clinical examination, or by it a diagnosis may be made without such preliminary examination. Thus at the present time consumption of the lungs may be microscopically diagnosed by an exami nation of the sputum, though the patient be 1,000 miles away, and in the same manner a number of diseases of allied forms may be recognized by certain minute evidences inter pretable by the microscope.
The most important of the intestinal para sites that can be thus identified are the tape worm, roundworm, hook-worm, fluke-worm and pin-worm. In all of these the physician df the present time, by a microscopical examina tion of the faces, can detect the presence of the eggs of the different kinds of worms and make a definite diagnosis. It is not necessary for parents to guess at the presence of worms and to treat their children 'ion suspicion.' The presence or absence of worms can be accurately and definitely determined by a competent micro scopist. Not only can a diagnosis of worms in general be made, but the precise kind of worm can be known by the characteristic configura tion of the eggs. Examination of the feces by the microscope can further detect various forms of indigestion and various kinds of inflamma tion in the intestinal tract.
As already indicated, tuberculosis can be told by an examination of the sputum, and the bacillus of tuberculosis can also be identified if it invades other organs of the body, notably the skin, bladder, kidneys, etc. The presence of tuberculosis in milk can also be demon strated by the microscope. The influenza bacil lus, the bacillus of diphtheria, the organism of cholera, of dysentery, of malignant pustule, of blood-poisoning, of pneumonia, of actinomy cosis, etc., can all be identified by a micro
scopical examination, as also can a number of diseases due to animal parasites in the body, other than intestinal worms. Thus there is no excuse for the general diagnosis of malaria unless the exact confirmatory evidence of the malarial parasite is found in the blood. The presence of Trichina in the body can also be learned by the peculiar changes that take place in the blood, and the blood-parasite Fslaria (see FU.ARIASIS), which causes a variety of conditions in the tropics, is recognizable under the microscope. Further, the microscopical examination of the blood itself offers a large field for clinical microscopy; a field which is very rapidly widening and offering increasing evidence of the value of this class of exam ination. There are many blood-diseases, per se, which can be diagnosed by simple examination. Anaemia and pernicious anaemia are important examples. Moreover, most of the acute in fectious diseases cause certain changes in the blood which may be utilized in microscopical work for diagnostic purposes. The Widal ag glutination reaction in typhoid fever is an important development in this line. Other agglutinating reactions are of immense import ance in medico-legal work. These blood changes are of a very definite character and have been studied by physicians the world over. Because of their peculiar technical nature they lend themselves to charlatan misinterpretation and serve as a basis for many quackish advertisers.
Microscopical examination of the urine has long been practised. By it various forms of disorder of the bladder and of the kidney can be told, and both renal disease and bladder disease can be detected long before such troubles become chronic and dangerous. In much the same manner the microscope can be used to examine other secretions and excretions of the human body — the secretions from the nose, the vomit, the exudates in pleurisy, exu dates in meningitis and peritonitis, etc.— and in the study of drinking-water, milk and food stuffs. In fact there is no branch of medicine in which definite and far-reaching results have not been obtained by means of the microscope. Consult von Jaksch, 'Clinical Diagnosis' ; Simon, 'Clinical Diagnosis' ; Ewing, 'Pathol ogy of the Blood' ; and Cabot, 'The Blood.'