4. =Diagnosis.= After the pathologic changes have been fully studied, the diagnosis should be formulated. If the pathologic changes found can be correlated as factors in some specific conditions they should not be considered separately, but the specific condition itself would constitute the diagnosis. When the pathologic conditions have no definite relation to each other they should be classified separately. If a section of kidney shows cloudy swelling, congestion, œdema, small-celled infiltration, hæmorrhage and casts, these different conditions would all be included in the diagnosis of an acute parenchymatous degenerative nephritis. If the general picture corresponds to that of tuberculosis, syphilis, neoplasm, etc., the various associated changes need not be considered alone, but the broad and comprehensive diagnosis should be expressed in as concise terms as possible. Written descriptions of microscopic appearances should be so full and clear that it is possible to make a diagnosis from the word-picture. A full and adequate analysis of the preparation set forth in concise and clear language is of more objective value than the bare diagnosis. Reproductions by means of drawings are also of great value in assisting the memory or in communicating the results of the observation to others. A technique sufficient for ordinary purposes may soon be obtained. Color work is usually easiest, since the majority of sections are stained in color. The camera lucida or Edinger’s drawing apparatus may be of great service in the enlargement and placing of the various elements of the section; with these instruments but little practice is necessary to produce rapid and accurate representations. The close inspection of the preparation during the drawing often reveals features that previously had escaped attention. Many workers object to drawings on the ground of subjectivity, but the same criticism applies even more to word-descriptions. Especial attention must, however, be paid to this danger, both in the case of drawings and word-descriptions. In the case of scientific work the written description is best backed up by photographs, rather than by drawings. Microphotography has the very great advantage of being purely objective, although dishonest photographs are possible. There are, however, certain limitations to microphotography. Differential details are lost in sections; all parts of the section cannot be fairly represented; and focal and color limitations are great disadvantages. I believe, however, that for pure scientific work word-descriptions should be accompanied by objective microphotographs instead of drawings. The microphotographic outfit of Zeiss has already been recommended as the best. It is impossible to take up the subject of microphotographic technique in this book. The reader is referred to the chapter on “Microphotography” in Aschoff and Gaylord’s Atlas, and to the works of Cresbie, Bagshaw, Kaiserling, Neuhauss, and others. (See article