HISTOLOGICAL DEMONSTRATIONS. 55 



c. Add magenta. The fluid stains and kills them. The 

 latter effect is probably due to the alcohol contained in the 

 solution. When dead, they exhibit only Brpwnian move- 

 ment. The direction of this movement is indefinite. The 

 movement of the elongated bacteria in a definite direc- 

 tion results from contractility. 



Examine the stained pellicle. The young granular bac- 

 teria are brightly tinged, while the jelly that surrounds them 

 is very faintly so. 



If the elongated bacteria, after staining with magenta, be carefully 

 examined with a i-25th inch lens, it may be seen that, as in the stained 

 torula already examined, there is a brightly-stained matter in the centre, 

 enclosed in a substance that remains colourless. The enclosed matter 

 is doubtless protoplasm, and the enveloping substance is probably cel- 

 lulose, because, like cellulose and unlike any soft albuminoid matter, 

 it is unaffected by a solution of caustic potash. Dallinger and Drys- 

 dale (Monthly Microscop. Journ. vol. xiv. p. 105) have detected a 

 minute fiagellum or cilium at the end of the bacterium, which acting 

 like the tail of a fish propels it through the fluid. 



67, 68, 69, and 70 are examined because of the fre- 

 quency of their occurrence in the urine and other fluids 

 examined by the medical microscopist. 



BLOOD. 



71. Blood of Newt. (H.) Stun the animal, dry the 

 tail, snip a piece from its extremity, and then express a small 

 drop of blood upon a slide. Place the cover-glass upon it 

 immediately. 



a. The coloured corpuscles. Shape when seen in front 

 face and in profile. Size. Border. Colour. Transpar- 

 ency. Contents. Observe that the corpuscles at first appear 

 to be homogeneous, but that, after a time, a light oval spot 

 appears in the centre of many ; this is the position of the 

 nucleus. 



b. The white corpuscles. There are several varieties of 

 these. Some are very finely granular nucleated masses of 

 protoplasm, as large, or even twice as large, as the coloured 

 corpuscles. These are the common white corpuscles. 

 Others are coarsely granular. These are not nearly so 



