492 APPENDIX 



examine a drop of the emulsion. It will be seen to consist of 

 innumerable fine drops of oil, which remain separate from one 

 another. If oil be shaken up with saliva or with artificial gastric 

 juice no emulsion will be formed, the oil soon separating. 



CHAPTER XV 



Directions for obtaining and studying blood corpuscles are 

 given in the notes on Chapter VIII. Sufficient blood to show 

 the phenomena of clotting may be obtained by chloroforming 

 a rabbit or a fowl, cutting one of the veins in the neck, and 

 catching the blood in small tumblers or beakers. 



CHAPTER XVI 



The beat of the heart is very conveniently studied in the 

 frog. Put a live frog into a glass bowl with a piece of cotton 

 batting or of cloth saturated with chloroform, and cover the 

 bowl. In a few minutes the animal will have become motion- 

 less and insensible. Remove it from the bowl ; with a sharp 

 knife divide the skin and cartilage at the base of the skull, thus 

 making an opening into the brain cavity ; into the latter thrust 

 a wire, and by twisting it about destroy the brain. The frog 

 will probably struggle, but its motions are reflex, and it has no 

 consciousness of pain. The heart may now be exposed by 

 making an incision through the skin and muscles of the upper 

 part of the abdomen and removing the cartilaginous part of the 

 breastbone. The heart will be seen beating inside the pericar- 

 dium. The latter may be removed and the heart freely exposed. 

 After studying the movements of the organ it may be removed 

 from the body by cutting the blood vessels close to their junc- 

 tion with the heart, and placed on a plate of glass or in a watch 

 glass containing .75 per cent salt solution. Its movements will 

 continue a long time after its removal from the body. The 

 organ may afterward be opened and the relation of its ventricle, 

 auricles, and the connecting veins and arteries studied (Fig. 273). 



