282 DIGESTION, CIRCULATION, AND ABSORPTION 



2. What is the use of fibrin ? 



3. What is serum? 



4. What is the composition and use of blood plasma? 



5. What is the function of plasma? 



6. What are the chief functions of blood ? 



Special Reports 



1. The work of the white corpuscles in destroying disease germs. 



2. The necessity of a liquid medium for carrying supplies to the cells 

 (" citizens ") of the body, and for carrying away the waste. 



3. The importance of coagulation. 



4. The composition of the blood. 



5. The life and work of Harvey. 



6. The function of blood plasma. 



References 



Hunter, Essentials of Biology. Chap. XXVI. 

 Hunter, Elements of Biology. Chap. XXIX. 



PROBLEM XLIX 



A study of the circulation of the blood. 



Materials. Living frog, tadpole, or fish partly affected with 

 ether, chloroform, or 1 % solution of chloretone, and mounted 

 on a shingle having a i-inch hole bored in one end, over which 

 is placed the web of the hind leg of the frog or the thin part 

 of the tadpole's tail or a fin of a fish. Keep the specimen 

 wrapped in a moist cloth, and the part observed moist. Or 

 use a chick embryo of 36 to 72 hours. Open the egg under 

 a saline solution (.7 per cent NaCl at 38 C.). Remove the 

 germinal disk with small dissecting scissors and float it out in 

 a watch glass. Use low power here, with both low and high 

 powers as needed for the rest. 



a. Living Specimen 



Observations. 1. Note a network of small tubes with mov- 

 ing disks, partly obscured in the frog by many dark-colored, 



