PROBLEM 199 



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preserve it. We have said that blood is made, in part at least, of 

 digested foods. In the bottle containing the clotted blood notice 

 the solid part, the clot, and a yellowish liquid called serum. 



Pour off some of the serum into each of three test tubes. 



Test the first with iodine solution. Result ? 



Test the second with Fehling's solution. Result? 



Test the third with nitric acid and ammonia. What is the 

 result? 



Test some of the blood fibrin with nitric acid and ammonia. 



Observations. Note what happens in each of the three tubes. 

 What is fibrin? 



Conclusion. 1. What nutrients are present in blood serum? 



2. Of what is fibrin composed? 



3. What nutrients are present in blood? 



NOTE. The blood clot is composed in part of structures (largely protein) 

 known as corpuscles. These can better be seen in prepared specimens under the 

 compound microscope. 



Problem 199 : To study the corpuscles of the blood. 



a. In Frog 



NOTE. Blood is composed of two principal parts, solid bodies (corpuscles) 

 and a liquid (plasma). 



Materials. Frogs, glass slide, cover glasses, microscope. 



Method. Place some frog's blood on a glass slide, cover and 

 examine under a compound microscope. 

 (See figure.) 



Observations. What are the color 

 and shape of the corpuscles that are most 

 numerous and most easily seen? These 

 are red corpuscles. 



There are other irregular-shaped cor- 

 puscles, more transparent and not so 

 easily seen. These are the colorless cor- 



^ CORPUSCLE OF FROG. 



puscles. 



Conclusion. 1. What kinds of corpuscles did you find? 

 2. Are corpuscles cells f Can you prove your statement? 



