LABORATORY EXERCISES 407 



Page 127. Prepared slides of blood are very useful here ; see address 

 list of dealers. 



Page 129. Arrangements may be made with a butcher to fill a pint 

 glass container with fresh blood; this should be set aside immediately 

 and left undisturbed until the blood has completely clotted. The less 

 the specimen is disturbed before being shown in a classroom, the better. 

 The serum will appear as a clear fluid about the clot; the latter will 

 shrink, but will retain the shape of the container. Clean fibrin can be 

 obtained by kneading a clot in water ; the longer it is washed the better. 

 It can then be preserved in 4% formalin, for use at any future time. 



Page 131. Dealers will furnish prepared slides of numerous sorts of 

 bacteria, including the types here mentioned. They also furnish slides 

 of blood showing the malarial organism, Plasmodium malariae. 



Page 133. It will be worth while to procure and show " wrigglers " 

 and pupae of mosquitoes, as well as adults, or parts of them, under low 

 power lenses. The young are easily obtainable, as a rule, from any woods 

 pond in early spring. Prepared slides of mosquito mouth parts are pur- 

 chasable. 



CHAPTER X 



Page 137. Obtain a turtle if possible, as it will show more satisfactorily 

 than any other animal the external events of a heart-beat. Action con- 

 tinues a long time after the head is removed. 



Page 138. If time and opportunity permit, the teacher may show the 

 heart of a beef or calf to the class, demonstrating the structure and action 

 of this organ. Instructions should be given the butcher to leave the blood 

 vessels connected with the heart long, i. e. the pulmonary artery and the 

 aorta should be severed not less than five inches from their exit from the 

 heart. The pericardium should be left on. 



Before class period the specimen should be trimmed of all rough ends of 

 tissues ; the blood vessels should be nicely dissected out from the mass of 

 tissue which surrounds them; in doing this the pericardium will be cut 

 away in part, but should be left cs perfect as possible. The external 

 appearance of auricles and ventricles, the elasticity of the blood vessels, 

 the contrast between arteries and veins, will be easily noted. If the follow- 

 ing order of procedure is observed, practically every feature of anatomy 

 and function of the internal parts can be readily shown. 



Cut away the pericardium. Shut off the pulmonary artery with a 

 strong clamp, as far from the heart as possible. Cut through the wall of 

 the right ventricle toward the apex of the heart ; carry this cut forward 



