18 THE ESSENTIALS OF HISTOLOGY. 



LESSON IV. 



STUDY OF THE BLOOD-CORPUSCLES OF AMPHIBIA. 



1. MOUNT a drop of newt's blood obtained from the cut end of the tail. It 

 may be allowed to mix with a very small quantity of salt solution. Examine 

 with the high power. Notice the shape of the coloured corpuscles both when 

 seen flat and edgeways, and the nucleus within each. 



Measure ten corpuscles (long and short diameters), and from the results 

 obtain the average dimensions of the newt's blood-corpuscle. 



Notice also the colourless corpuscles, smaller than the red, but considerably 

 larger than the pale corpuscles of human blood, although otherwise resembling 

 these. 



Sketch two or three red corpuscles and as many white. 



Be careful not to mistake the liberated nuclei of crushed red corpuscles for 

 pale corpuscles. 



Enormous cells and nuclei belonging to the cutaneous glands as well as the 

 granular secretion of those glands may be present in this preparation. 



2. Apply a drop of water to the edge of the cover-glass of the same pre- 

 paration and notice its action upon the corpuscles. 



Sketch two or three corpuscles altered by the action of the water. 



3. Mount another drop of blood, and apply dilute acetic acid (1 per cent.) 

 instead of water at the edge of the cover-glass. Make sketches showing the 

 effect of the acid upon both red and white corpuscles. 



4. Examine the corpuscles of newt's blood which has been allowed to flow 

 into boracic acid solution (2 per cent.). Notice the effect produced upon the 

 coloured corpuscles. Sketch one or two. 



The coloured blood-corpuscles of amphibia (fig. 16), as well as of 

 most vertebrates below mammals, are biconvex elliptical disks, consider- 

 ably larger than the biconcave circular disks of mammals. 1 In addition 

 to the coloured body of the corpuscle, which consists, as in mammals, of 

 haemoglobin inclosed within an envelope, there is a colourless nucleus, 

 also of an elliptical shape, but easily becoming globular, especially if 

 liberated by any means from the corpuscle. The nucleus resembles 



1 The following are the dimensions in parts of a millimeter of some of the cor- 

 puscles of oviparous vertebrates : 



Long diameter Short diameter 



Pigeon . . . 0-0147 0'0065 



Frog . 

 Newt . 

 Proteus 

 Amphmma . 



0-0223 0-0157 



0-0293 0-0195 



0-058 0-035 



0-077 0-046 



