【摘要】
Passage Two
One of the most important fields in veterinary medicine is medical research. Experiments with animals have led to discoveries that save many human lives. Cancer, heart disease, and other crippling illnesses are studied in animals. Vaccines and serums are always tested on animals before they are used on humans. Vaccines for tetanus, measles, and polio were used first on animals.
Veterinarians have made many life-saving discoveries. For example, the research of one veterinarian, on the sweet-clover disease in cattle, led to the discovery of dicoumarol. Dicoumarol prevents blood from clotting and is used in treating human heart disease.
Veterinarians have made many contributions to the exploration of space. Dogs, mice, and chimpanzees are often used to test the effects of varying atmospheric pressure on animal life before human beings are sent into space. Veterinarians study the animals carefully for the effects of space travel on their bodies. The results of these studies are used in preparing men to go into space and contribute to the safety of the astronauts.
Veterinarians share responsibility for the health and safety of our food. Their work in the cure and prevention of animal diseases has done a great deal to ensure us wholesome poultry, meat, and milk.
Veterinarians are also important in the fur industry, for animals must be healthy and well cared for if they are to grow glossy coats. Veterinarians are needed to take care of the animals in zoos and circuses. At racetracks, they inspect the dogs and horses to make sure that they have not been drugged or abused. Frequently, veterinarians are employed by the government to treat and study the wildlife in national parks and game preserves.
Questions 30 to 32 are based on the passage you have just heard.
30. Which is the most important field in veterinary medicine?
31. Before sending astronauts into space, what must be done in advance for veterinarians in a veterinary lab to help to test the safety?
32. According to the passage, for what kind of animals do veterinarians not take necessary responsibility?