64 ANIMAL BIOLOGY. [Part I. 



1. Blood and Lymph. Examined under the microscope (high 

 power), the blood is seen to consist of a colourless fluid, the 

 plasma, in which float a great number of yellowish red corpuscles 

 and a few white corpuscles. The red corpuscles of the frog (Fig. 

 24, i. b) and the pigeon are flattened slightly bi-convex oval discs, 

 and contain a nucleus. Those of the rabbit are circular bi-concave 

 discs (Fig. 24, i. c) and contain no nucleus. The size of the 

 corpuscles is, in the frog, g-^- inch ; in the pigeon, Y J^ ; in the 

 rabbit, -g^Vo"- Treated with dilute acetic acid, the nucleus (when 

 present) becomes more obvious, the colour of the surrounding 

 parts of the corpuscle is gradually discharged, and eventually 

 that of the nucleus also. If a needle be rapidly drawn across a 

 drop of blood, some of the cells will be cut in two. There is 

 no escape of the contents from the cut halves, showing that they 

 are composed throughout of a viscid material, and not of a fluid 

 contained within a membranous wall. The manner in which 

 the corpuscles recover their shape after distortion by pressure 

 may be seen in the capillaries of the living frog (see p. 60). 



The white corpuscles (leucocytes) are of much the same size (^-Q-Q 

 inch) in frog, pigeon, and rabbit, and are in all cases nucleated. 

 On a cold slide they will probably appear round ; but if the 

 slide be warmed they will show amoeboid movements, the proto- 

 plasm flowing out into irregular processes and slowly creeping 

 over the slide (Fig. 24, i. a). Sometimes they divide by fission. 

 The nucleus first splits into two, and then the two halves of the 



If borax-carmine be used, transfer it to 70 per cent, alcohol, to which a few 

 drops of nitric or hydrochloric acid have been added. 



5. After staining, place for an hour in 80 per cent, alcohol, and then in 

 absolute alcohol for another hour. 



6. Place in spirits of turpentine for an hour, and then transfer to paraffin 

 (sold of proper hardness for this purpose of imbedding), which should be kept 

 just melted. Leave for six or eight hours, and then cast in a mould. The small 

 oblong vessels in which moist water-colours are sold answer well, Arrange the 

 specimen with warm needles. 



8. Pare away the paraffin so as to bring the object into view. Cut the thinnest 

 sections you can get with a sharp razor. 



9. Dissolve the paraffin in turpentine. 



10. The section may now be examined or mounted permanently in Canada 

 balsam. 



