THE MICROSCOPE IN PATHOLOGY. 227 



perfects pathology, and guides to right conclusions the 

 seeker after positive truth in medicine. 



Our plan forbids an extensive outline of the facts of 

 morbid anatomy. We propose merely such a classifica- 

 tion of the microscopic appearances of diseased structures 

 as may serve to guide the student and busy practitioner 

 in actual observation. 



PREPARATION OF SPECIMENS. 



Much may be learned by the examination of a patho- 

 logical specimen without any preparation whatever, or 

 with the use of indifferent fluids (see Chapter V). A thin 

 section may be made under water with a Valentin's knife, 

 or a small portion may be snipped off with curved scis- 

 sors and teased with fine needles. The freshly-cut sur- 

 face of tumors may be gently scraped with a knife and 

 the separated elements examined in glycerin and water. 



For a thorough examination it will be necessary to 

 harden, stain, and make thin sections, as described in 

 Chapter V and at page 224. Mtiller's fluid, page 68, will 

 be found most generally useful for morbid specimens. 

 After small pieces have lain some time in this they can be 

 still further hardened by absolute alcohol. Before cut- 

 ting thin sections, either by hand or with a section-cutter, 

 the specimen will require to be imbedded so as to be 

 readily held and cut without tearing. A mixture of wax 

 or paraffin and olive oil is generally used of such consist- 

 ence as will indent readily with the thumb-nail when 

 cold. For very delicate tissues, saturation in a mixture 

 of glycerin and gum arabic, made perfectly clear and vis- 

 cid, so as to be easily drawn out into threads, is useful. 

 After saturation the specimen is thrown into alcohol, 

 which hardens the gum and fixes the tissues so as to be 

 readily cut. The thin section can be thrown into water, 

 or carmine solution, to dissolve the gum, and the stained 



