64 



this baud, and with a sharp pair of scissors cut through the 

 right and left aortae, the pre and post caval veins, and the 

 surrounding tissue, taking care not to injure the sinus 

 venosus. Place the heart in a watch-glass, moistening 

 occasionally with normal saline solution.' The beats will 

 not be interrupted at all, or for a very short time onl}'. 



290. Watch the beating of the heart. Do the auricles and 

 ventricle contract simultaneously ? What are the number of 

 beats per minute ? 



291. Lift up the apex of the ventricle, and with the 

 scissors cut off the apex at the upper third of the ventricle. 

 Watch the separated portions. Is there any difference in 

 the beating ? 



292. With the .scissors separate the two auricles from each 

 other, letting the attached p9rtion of the ventricle remain to 

 each auricle. Do they continue to beat? 



293. The .same frog, if it has been kept in a moist place, may 

 be u.sed for the following cilia experiment : Place the frog 

 upon its back, and cut through the lower jaw, along the mid- 

 line, continuing the incision down the oesophagus as far as the 

 stomach. Pin the parts back and moisten the mucosa with 

 normal salt .solution, if it is at all dry. Place a small, thin 

 piece of cork upon the mucosa ju.st below the orbits, and 

 note that the cork is carried toward the stomach by the cilia. 

 Warm a little of the normal salt solution to 30° C. , and re- 

 peat the experiment. Apply heavier bits of substance to 

 the mucosa, and note if their positions are changed. 



294. If the caudal lymph-hearts are still beating, pass a 

 tracer or piece of wire down the spinal canal to destroy the 

 myel. If thoroughly destroyed the lymph-hearts will cease 

 to beat. 



'Made by dissolving 6.5 grams of sodium chloride in one liter of 

 distilled water. 



