124 LABORATORY MANUAL 



parts: the outer solid part, the cortex; the inner 

 striated part, the medulla. The slight elevations are 

 called pyramids of Malpiglii, between which small 

 tubes may be seen leading into the sinus. The tube 

 leading from the sinus is the ureter which carries the 

 excretion into the bladder. Notice the enlarged end 

 of the ureter in the sinus. Note also the entrance of 

 the renal artery and the renal vein into the kidney 

 just above the ureter. The artery brings in the blood 

 which gives up its waste in the kidney. This waste is 

 collected by the tubules and emptied from the sinus 

 into the ureter. The capillaries collect the blood which 

 has been cleared of waste and return it to the vein. 



Exercise 83. The Skin. 



Object: To study the structure and functions of the 

 skin. 



Apparatus 



Plaster model of skin 



Directions : A. External structure : The outer 

 layer of the skin is called the cuticle, .or the epidermis. 

 What is its color ? Thickness ? Where is it thickest on 

 the hand? What markings do you find on it? Can 

 you find the pores, openings of the sweat glands ? Does 

 the epidermis contain blood vessels? Does it contain 

 nerves ? 



B. Internal structure : From the plaster model, or 

 a prepared slide of the skin, note the two layers 

 comprising it. Note the epidermis again. What is its 



