GENERAL STRUCTURE. 17 
all large arteries, and also aid by their contraction in moving 
the lymph through the numerous lymphatic vessels extend- 
ing from the extremities to the jugular veins. 
These systems previously described are capable of per- 
forming their functions only when supplied with nerves 
through which impulses can be transmitted from the brain 
and spinal cord. Stimuli sent by the brain or cord through 
the nerves cause the gastric juice to flow into the stomach, 
the bile and pancreatic secretions to be formed and poured 
forth into the intestines, the kidneys to eliminate the waste 
from the blood, the heart to beat, and the muscles to contract 
and relax. 
The only system which is not absolutely necessary to the 
life of the cat is the reproductive; but this is required for 
the continuance of the species. It is not, however, func- 
tional during the entire life, but as a rule only from the 
end of the first to the tenth year. 
PRACTICAL QUESTIONS. AND SUGGESTIONS. 
t. What advantages are derived from the study of mammalian 
anatomy ? 
. Define morphology and state a fact from that science. 
What two sciences does biology include? 
. What five sciences are included in zoology? 
. Make a physiologic statement concerning the heart. 
. State five facts belonging to the science of distribution. 
What is taxonomy? 
. Name five classes of vertebrates. 
9. By examining specimens discover what external feature distin- 
guishes a reptile from an amphibian. 
10. Do all mammals have hair? 
11. What habit is common to no other vertebrates except mammals? 
12. Give two points of difference between the two subclasses of 
ON AnNRwWDN 
Mammalia. 
13. Name the ten orders of Eutheria and give an example of each. 
14. Which orders derive their names from the habits of the animals? 
15. Which orders derive their names from anatomic features? 
16. Which orders are aquatic? 
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