ANIMALS. 143 



determined ? Is the manurial value of the same variety of food 

 always the same ? Are the manurial substances of the same value 

 in whatever food they are found ? Name articles of food which 

 have a high manurial value. Wha is the difference between the 

 manurial value of food, and the value of the manure from the food ? 

 What items must be deducted from the one to obtain the other? 

 What circumstances increase and diminish this difference ? 



What are the two values of food ? How is the true cost of food to be 

 reckoned in farming ? Name articles which cost but little accord- 

 ing to this method of reckoning. 



What is the purpose of digestion ? Do plants digest their food, like 

 animals? How does digestion begin in the mouth? What is the 

 saliva ? How fast is it formed ? Explain the action of the stom- 

 ach. Describe the intestines. How long are they ? What becomes 

 of the food after it is digested ? 



Name the animals called "ruminants." Why is their digestive 

 system different from that of other animals ? What is the chief 

 difference? Describe the first stomach. WTiat is the second 

 stomach ? 



What service does the third stomach perform? Which stomach 

 corresponds to that of other animals ? Into which stomach does 

 the food first pass, when swallowed ? In what way is the " cud " 

 brought to the mouth ? Into which stomach does it pass when 

 swallowed again ? What may be the difficulty with animals unable 

 to chew the cud ? Why are ruminants able to live longer without 

 food than other animals ? 



What is the use of the blood ? In which parts of the body is it to be 

 found? Describe the system of tubes through which the blood 

 passes. Why does it pass through the lungs ? Of what does the 

 blood consist ? What is the purpose of the corpuscles ? From 

 what does blood derive its color ? Why is the color different in 

 different parts of the body ? 



What other office does the blood fill besides conveying nourishment 

 to the body ? Name the other waste products of the body besides 

 undigested food. Name the different methods by which they 

 escape from the body. 



How does an animal resemble a machine ? Why is one animal more 

 profitable than another for a given purpose ? For what two rea- 

 sons should the health of animals be cared for? 



