MILK. MOUNTING BY FLOTATION. 13 



decompose. Numbers of minute rod-shaped bodies (Bacteria) 

 appear moving through the fluid with an undulating or spiral 

 motion. They are propelled in a definite direction by a flagellum 

 at one or both ends ; these flagella are only revealed by the 

 highest powers. The bacteria are the causes of the putrefactive 

 changes in the infusion. 



Milk. A thin film (11) exhibits small spherical bodies (fat 

 globules) in great numbers, floating in a colourless fluid (milk 

 plasma). The globules are transparent and do not adhere to 

 each other. Irrigate with acetic acid and note the change 

 produced in the behaviour of the globules to each other. 



Newt's moult, Squamous epithelium. Mount a piece, 

 which has been preserved in alcohol, as follows : 



Flotation on water. Prop the object into a basin of water, the 

 effect of alcohol in unfolding and spreading out a thin film of tissue is 

 instantaneous, the tissue lies on the surface of the water. Pass a slide 

 two-thirds under water in a sloping position, guide the object to its 

 centre with a needle, and holding it there lightly, raise the slide from 

 the basin. Then turning the slide into the vertical position so as to 

 drain the water to one end, dry the slide with blotting paper on both 

 sides and right up to the edge of the tissue. 



Stain on the slide with haematoxyliri, * by adding a small drop 

 of the stain to an equal quantity of water on the slide and guiding it 

 over the preparation with a glass rod. Cover and watch the develop- 

 ment of the staining under the low power, and as soon as the nuclei 

 are sufficiently tinged, bathe off the superfluous colouring matter with 

 water, or float the tissue off the slide into the water and back on to 

 the slide. 



Mount in balsam which is the next step, dehydrate, by dropping 

 absolute alcohol, 6 or 7 drops successively, on the preparation, flowing 

 it slowly across it so as to give the alcohol time to abstract the water. 

 The next step is to dear with oil of cloves (or other essential oil) by 

 placing a drop of the oil on the slide and guiding it to the edge of the 

 object, it will flow beneath it, will soak up through the preparation, 

 and will render it translucent. This indicates that the oil has taken 



'Kleinberg's solution see appendix 20. 



