134 Living Things Are Basically Alike unit it 



5. What word do we use to state the fact that cells differ in shape and 

 activities? 



6. What are the four main kinds of tissues in a complex animal? State 

 which tissues are included in each group. Briefly tell the character- 

 istics of each type of tissue. 



7. Name two important plant tissues. 



8. Summarize this short problem in your own words. 



Exercises 



1. Is a bone a tissue or a collection of tissues? Obtain a beef or lamb 

 leg bone sawed lengthwise through the middle. Scrape it clean of meat. 

 Use a strong dissecting needle to detect the covering on the shaft (long 

 part) of the bone. Describe it. This is a kind of connective tissue. What 

 might be a function of this covering? Feel the substance, cartilage tissue, 

 that covers the head of the bone. Describe. Prick the inside of the head 

 of the bone with the needle. Describe this spongy bone. What makes it 

 red? This is known as red marrow. Prick the material outside the marrow; 

 this is true bone tissue. Feel the substance in the inside of the shaft. This 

 is yellow marrow. How does it differ from red marrow? Examine some 

 of the red marrow under the microscope. List all the substances vou have 

 found. Is the bone a single tissue or a collection of tissues? Of course, you 

 cannot see the bone cells with the unaided eye. Your teacher will give 

 you a prepared slide of bone tissue. Notice the long dark spots with manv 

 fine projections. They are arranged in concentric circles (circle within 

 circle) around a large round opening. In life, blood vessels and nerves 

 run through these circular openings. Each long spot with radiating pro- 

 jections is a space in which a bone cell used to lie. The protoplasm has 

 disappeared. 



2. Animal tissues may be studied easily by preparing slides of tissues 

 from a recently killed frog. 



Epithelial Tissue: (a) Squamous (flat). Frogs shed their skin continu- 

 ously. Place on a slide a bit of shed skin found in the water in which 

 frogs arc kept. If it tends to roll up be sure to unroll it by holding down 

 the edges with dissecting needles. Stain with Lugol's solution and cover 

 with a cover slip. Fxamine and draw the flat epithelial cells. (/;) Ciliated. 

 Remove a small piece of epithelium from the roof of the mouth of a 

 freshly killed frog. Make a cut with a scalpel in the region near the 

 eyeball and with your forceps peel it off. Aloimt the material on a slide, 

 add a drop of Ringer's solution and a cover slip. Observe the beating of 

 the cilia. 



Muscle Tissue: (a) Voluntary or striated. Cut into the muscle which lies 

 under the skin on the ventral side of a freshly killed frog. Strip off a 

 small piece with your forceps. Place on a slide and tease the muscle apart 



