PROBLl'.M 1<J9 2:53 



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 licjuid called .scnufi. 



Pour off some of the sermii 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 (larcely protein) 

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

 compound microscope. 



Problem 199 : To study the corjniscles 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- coupuscle of Fu..u. 

 puscles. 



Conclusion. — 1. What kinds of (•ori)iiscles did you find".' 



2. Are corpuscles cells? Can you provi* your statement? 



