Two main techniques have been used for
training elephants, which we may call respectively the tough and the gentle. The
former method simply consists of setting an elephant to work and beating him
until he does what is expected of him. Apart from any moral considerations this
is a stupid method of training, for it produces a resentful animal who at a
later stage may well turn man-killer. The gentle method requires more patience
in the early stages, but produces a cheerful, good-tempered elephant who will
give many years of loyal service. The first essential in elephant training is to assign to the animal a single mahout who will be entirely responsible for the job. Elephants like to have one master just as dogs do, and are capable of a considerable degree of personal affection. There are even stories of half- trained elephant A. can have unpleasant consequences later B. is the most effective method available C. increases the time it takes to tram the animal D. ensures loyal service for years to come [单项选择]Two techniques have recently been developed to simplify research and reduce the number of nonhuman primates needed in studies of certain complex hormonal reactions. One technique involves the culturing of primate pituitary cells and the cells of certain human turnouts. In the other, animal oviduct tissue is transplanted under the skin of laboratory primates. Both culturing techniques complement existing methods of studying intact animals.
With an in vitro culturing technique, researchers are deciphering how biochemical agents regulate the secretion of prolactin, the pituitary hormone that promotes milk production. The cultured cells survive for as long as a month, and they do not require serum, a commonly used culture ingredient that can influence cellular function and confound study results. One primate pituitary gland may yield enough cells for as many as 72 culture dishes, which otherwise would require as many animals. The other technique allows scientists to monitor cellu A. scientists can study the pituitary gland for the first time B. the procedures are simpler and require fewer laboratory animals C. the study of intact laboratory animals has now been rendered obsolete D. researchers were able to discover prolactin 我来回答: 提交
|