142 AMPHIBIA (the frog) 



(c) Size? 



(d) Use? 



(5) The Mesentery is a thin membrane which holds the 



intestines in place. 



(a) Does it contain any blood-vessels? 



(b) From what source do they come? 



(c) To what do they lead? 



(6) The Spleen is a small round red body in the mesentery. 



(a) Find and identify it. 



(b) Use in man? 



(c) Use in the frog? 



(7) The Intestines pass from the stomach to the vent. 



(a) Carefully cut the mesentery and unravel the intes- 



tines. Are they coiled or straight? 



(b) Are they of the same diameter, or do they vary 



in different portions? Where, and how much? 



(c) Length as compared with that of the body? 



(8) The Cloaca. This is the enlargement of the intestine 



just before it reaches the vent. The intestines, 

 kidneys, and reproductive organs open into it. 



(9) Sketch the alimentary canal from the mouth to the 



vent, properly locating and naming all its parts or 

 organs. 



2. The Respiratory Organs. 



(1) The lungs. How much of the body-cavity do the lungs 



fill when inflated? When not inflated? 



(2) The Trachea. Find the trachea and trace it to its 



branches, the bronchi, which lead to the lungs. 



(3) Sketch the respiratory organs and name all parts. 



3. The Circulatory Organs. 



(1) The Pericardium, around the heart. Its use? Care- 



fully cut through the pericardium and find the heart. 



(2) The Heart. 



(a) The Ventricle. The pointed posterior portion of the 

 heart is the ventricle. 



(1) Shape? 



(2) Color? 



(3) Size? 



(4) Use? 



