CHAPTER XIII. 



THE BACTERIOLOGICAL EXAMINATION OF 

 FLUIDS AND TISSUES. 



Section I. Film preparations, p. 203. 



1. Unstained preparations, p. 203. 2. Stained preparations : A. Preparation of 

 films (a) Fluids, p. 204; (6) Scrapings of organs, p. 205; (c) Sputum, p. 205. 

 B. Staining methods : (a) Simple staining, p. 205 ; (6) Differential staining, p. 207. 

 Section II. Histological preparations, p. 211. 



1. Instruments, p. 211. 2. Freezing methods, p. 212. 3. Paraffin embedding 

 methods, p. 212. 4. Preliminary treatment of sections, p. 215. 5. The staining of 

 sections : A. Simple staining, p. 216 ; B. Differential staining, p. 217. 



SECTION I. FILM PREPARATIONS. 



Pathological material whether taken during life or after death, from man 

 or from one of the lower animals, may be examined : 



1. either fresh and unstained, or 



2. after drying and staining. 



1. Unstained preparations. 



(a) Fluids. Blood, fluid exudates and pus may be collected in a Pasteur 

 pipette and ought to be examined at once. 



The examination of blood may be described in illustration of the method. 

 As soon as the blood is removed from the body a drop is placed on a slide 

 and covered with a cover-glass ; the blood spreads out in a thin layer between 

 the slide and cover-glass, and by pressing lightly on the latter the excess can 

 be squeezed out at the edges and wiped away with a piece of soft linen. In 

 this way a very thin uniform layer is obtained and must be examined imme- 

 diately (obj. D ; oc. 2 Zeiss). 



The slides and cover-glasses must be absolutely clean, because dirt or 

 grease prevents the blood from spreading in a thin and uniform layer, and 

 renders satisfactory examination of it impossible. It is also essential that 

 the red cells should not be heaped one on another, as this would mask the 

 presence of micro-organisms. 



Should the examination be very prolonged the edges of the cover-glass 

 may be luted with paraffin, but in the majority of cases this is unnecessary, 

 because the blood at the edges of the cover-glass, being in contact with the 

 air, coagulates and thus affords sufficient protection to the central parts of 

 the preparation. 



Serous exudates, liquid pus, etc., should be treated in the same way ; but if the 

 pus be inspissated it must be treated as though it were a scraping from an organ. 



