24 PRACTICAL HISTOLOGY [ill 



e. Some faint blue masses arising from the plate- 

 lets; these are not always seen as they quickly dis- 

 integrate. 



4. Fixing corpuscles by heat before staining. The haemo- 

 globin is dissolved out of the red corpuscles and the white 

 corpuscles are more or less altered in films treated with staining 

 fluids containing less than 75 p.c. alcohol. This sometimes 

 occurs with the 75 p.c. alcohol stains. To avoid such alteration 

 the corpuscles may be fixed by heat, before staining, thus : 



Place a dry film of blood for 2 to 5 min. at a temperature 

 of 110 C. This may be obtained by placing a Bunsen flame 

 under one end of a long strip of copper ; the part of the strip 

 which is at a temperature of 100 C. can be determined by 

 noting where a small drop of water boils ; the specimen should 

 be placed a little nearer the flame than this, the filmed side 

 undermost. (Instead of this, the cover-slip is sometimes passed 

 two or three times through the flame of a Bunsen burner.) The 

 corpuscles stain somewhat better after fixing, but they are apt 

 to sbiink and leave a clear space around them. 



The fixation of the haemoglobin in the corpuscles may be observed 

 later in sections of tissues hardened in osxnic acid vapour, osmic acid, 

 mercuric chloride dissolved in salt solution, Muller's fluid, formol. 



5. Platelets. Kill a rat or mouse with chloroform. Expose 

 the heart, and cut through the pericardium. Cut through the 

 ventricle and let one drop of blood fall into 6 c.c. of (a) osmic 

 acid and salt (11. 16), (6) methyl- violet solution (n. 17), 

 (c) 1 p.c. oxalate of potassium. Stir, centrifugalize, and examine 

 a drop for platelets. They are small, colourless, oval bodies, 

 J to ^ the size of the red corpuscles and without nuclei. 



6. "Wash the tip of the finger, place on it a drop of the 

 methyl-violet solution or of the potassium oxalate solution. 

 Prick the finger through the drop. As soon as blood comes 

 transfer to a slide and examine. 



