THE CRUSHED DROP — a method of preparation of drugs for microscopic examination of biological objects. In research practice of R. to. use during the studying of a form, the size and an arrangement of microorganisms, detection of mobility of bacteria, during the overseeing by growth and reproduction of microorganisms, for studying of reactions of microorganisms to chemical connections (chemotaxis) and physical factors. In practice of medical microbiology this method is applied at microscopic examination of material from patients to detection of causative agents of the diseases possessing specific morphology — protozoa, spirochetes, fungi. By method P. to. and use its modifications also at microscopic examination a calla and other allocations on eggs and larvae of helminths.
For preparation of drug prepare a suspension of the studied material in isotonic solution of sodium chloride or mains water, adding the substances facilitating process of microscopy (dyes, clarifiers, etc.); use also cultures of microorganisms on fluid or semi-fluid mediums, biol, liquids. The drop of material is placed on a slide plate and from above put cover glass, avoiding emergence in drug of air traps. Liquid shall not support limits of cover glass. The crack between subject and cover glasses can be pressurized by vaseline or the mix consisting of equal volumes of vaseline and paraffin. At a research of fast-moving microorganisms to reduce the speed of their movement to suspension it is possible to add methyl cellulose. In this case it is possible to observe the movements of flagellums. At microscopy of living cells use of intravital (vital) dyes — methylene blue, neutral red and others (in cultivation 1:1000 — 1:10 000), the drugs increasing contrast and allowing to reveal interior of protozoa, fungi, etc. is possible.
Depending on an object and the purposes of studying the microscopy can be carried out at small or big increase with dry or immersion systems. In the elementary case the microscopy is carried out in the darkened field of vision at the narrowed diaphragm and the lowered condenser. More sharp image is given microscopy in a dark field of sight, phase and contrast or anoptralny microscopy (see. Microscopic methods of a research ). At preparation of drugs thickness of slide plates shall not exceed 1,2 mm, and thickness of cover glasses — 0,17 mm. Slide and cover plates shall be pure and fat-free. At microscopy in a dark field of sight drug is prepared as it is possible more thinly, and thickness of cover glasses shall not exceed 0,11 mm.
See also Bacteriological techniques .
Bibliography: Meynell D. and Meynell E. Experimental microbiology, the lane with English, M., 1967; Practical parasitology, under the editorship of D. V. Vinogradov-Volzhinsky, L., 1977; The Guide to microbiological diagnosis of infectious diseases, under the editorship of K. I. Matveev, M., 1973.
S. S. Belokrysenko.