PROBLEM 219 247 



kidney. Get the butcher to leave the mass of fat around the kid- 

 ney. Of what use might this fat be ? Notice, after removing the 

 fat, that the kidney appears to be closely wrapped in a thin coat 

 of connective tissue; this is called the capsule. Remove the 

 kidney from this capsule. Notice its color and shape. The de- 

 pression called the hilum is deeper than the corresponding region 

 in the kidney bean. The hollow tube passing out from this region 

 is called the ureter. Blood vessels also enter and leave the kidney 

 at the hilum. Cut the kidney lengthwise into halves. Try to 

 find the following regions : (1) the outer or cortical region; note 

 its color ; (2) the inner or medullary layer ; this layer is provided 

 with little projections; these are the pyramids of Malpighi, so 

 called after their discoverer, Marcello Malpighi, a celebrated 

 Italian physiologist; (3) the cavity or pelvis of the kidney. At 

 the summit of each pyramid is a small opening through which 

 escapes into the pelvis the secretion formed in the little tubules 

 in which the real work of excretion is performed. 



Conclusion. 1. Where is the waste taken from the blood in 

 the kidney? (Study the diagram on page 341, Civic Biology.) 



2. Where does this waste pass out of the body? 



Problem 219 : The skin as an organ of excretion and heat 

 control. 



Materials. Model of human skin in section, thermometers, 

 hand lens, jars, scales. 



a. Structure 



Method. Examine the model of a cross section of skin. 

 Locate (using your Civic Biology, page 342) the epidermis, 

 dermis, sweat glands, oil glands, nerves, and blood vessels. 



Observations. Where is the epidermis and what structures 

 does it contain? Examine the surface of your skin with a hand 

 lens. What structures are found in the dermis? 



Conclusion. How might the above-mentioned structures be 



of value to the body? 



b. Functions 



The above question may be answered in part by the following 

 experiments made at home or in the laboratory. 



