46 LIVING MATTER OR PROTOPLASM. 



6. Place a sprig of Anackaris, Laving cut its stem squarely 

 across, in a test-tube with fresh water (not distilled), and hold it 

 in the sun-light. In successful experiments hubbies of oxygen 

 come forth from the cut end at regular intervals. (It is neces- 

 sary to have vigorous plants, and usually a number of sprigs must 

 be tried.) These bubbles are produced by the chemical action of 

 protoplasm, aided by chlorophyll (see p. 85). Count and record 

 the number of bubbles per minute. 



7. Without changing the illumination, immerse the base of 

 the test-tube in iced water. Interpret and record your results. 



8. Without moving the apparatus, gradually heat the water. 

 Count and record the number of bubbles at different tempera- 

 tures (e.g., 10, 20, 30, 40, 50, C.). Note at what tempera- 

 ture the bubbles cease. 



G. Rigor Caloris. 



Immerse in a beaker of water at the ordinary temperature 

 the hind limbs of a recently-killed frog. (Both brain and spinal 

 cord should have been destroyed.) Heat the water gradually, and 

 note by means of a thermometer the temperature at which the 

 limbs stiffen, become rigid, and violently extended. 



H. Rigor Mortis. 



Examine an, animal which has passed into the death-stiffening. 

 This is regarded as a consequence of coagulation taking place at 

 or near the time of the death of the muscles. 



Compare with an animal in rigor caloris (G.). 



Compare both with fresh living muscle from the leg of a de- 

 capitated frog. 



I. Moisture. 



1. Wipe dry with a towel or filter-paper a frog which has 

 been killed by the demonstrator; then weigh, and place it in a 

 warm bath made for drying at 100 C. If this be not at hand 

 a hot-air register or radiator will answer. After a day or two 

 weigh again, and calculate the loss of weight, actual and percent., 

 caused by drying. This represents approximately the amount of 

 water originally present. 



2. Repeat the experiment, using instead of a frog a lettuce- 

 head, a bunch of celery, a mushroom, a leaf, a potato, or any fresh 

 and succulent vegetal structure. Compare the results with (I). 



