112 PRACTICAL HISTOLOGY. [ll. 



with paraffin wax by heating a wire bent at right angles to melt 

 the paraffin and applying it along the edges of the cover-glass. 



Ranvier uses a moist air-chamber (fig. 70). In the centre of the 

 chamber is a small piece of glass, less in height by -^th of a milli- 

 metre than the height of the walls of the cavity. The fluid con- 

 taining the corpuscles is placed on this, covered with a cover-glass 

 which is sealed down by means of paraffin wax. The object is thus 

 protected from evaporation, while it has in relation to it a layer 

 of air. 



14. Acetic Acid (i per cent.). On irrigating a fresh preparation 

 with dilute acetic acid, the protoplasm is made clear and transparent, 



and the complex nucleus 

 usually consisting of three 

 parts, and hence called tri- 

 partite is distinctly re- 

 vealed (fig. 71, a). If the 

 acid act vigorously, it may 



FlQ. 7 i.-a. Action of Acetic Acid on the Colourless ^ e almost impossible to SCO 



Blood-Corpuscles of a Frog. Action of Water the Outline of the HOW clear 

 on the Colourless Blood-Corpuscles of a Frog. i 



6. Early, and c. Later Stages. protoplasm. 



15. Water. On irrigat- 

 ing a fresh preparation with water, the colourless corpuscles are 

 killed, and they assume a globular form, the protoplasm becoming 

 at first more granular (fig. 71, ft), and subsequently clear and trans- 

 parent, thus distinctly revealing the presence of the nucleus. The 

 granules may exhibit Brownian-movements, while each cell has an 

 outline round it as if a membrane had been formed round it. So 

 that by the addition of water these corpuscles may be changed so as 

 to resemble salivary corpuscles (Lesson IV.). 



16. Magenta. This stains the nucleus deeply and the proto- 

 plasm to a less degree. 



For Fibrin (Lesson III. 



Lymph. 



17. (a.) Pith a frog, and with a fine pipette withdraw a little 

 lymph from the dorsal lymph sac, or, better still, curarise a pithed 

 frog, and next day remove the lymph from its sub-lingual lymph 

 sac. The lymph accumulates there in large amount. 



Lymph (H). 



(a.) Observe numerous leucocytes, mixed perhaps with a few red 

 blood-corpuscles, exactly like the three varieties of leucocytes found 

 in the blood. A coagulum of fibrin will ultimately be formed. 



(ft.) The toad yields a very large quantity of lymph. Destroy 

 its brain, wipe one leg dry, and cut off the projecting toe. At once 

 large drops of lymph flow out, which soon coagulates (S. Mayer). 



