【正文】 ilizedmen like such a way of living. While they enjoy the fort and banal luxury of their dwelling, they do notrealize that they are deprived of the necessities of life. The modern city consists of monstrous edifices and ofdark, narrow streets full of petrol fumes, coal dust, and toxic gases, torn by the noise of the taxicabs, lorriesand buses, and thronged ceaselessly by great crowds. Obviously, it has no been planned for the good of itsinhabitants.劉曉華 liuxiaohua72@18Lesson 17 A manmade diseaseIn the early days of the settlement of Australia, enterprising settlers unwiselyintroduced the European rabbit. This rabbit had no natural enemies in the Antipodes,so that it multiplied with that promiscuous abandon characteristic ofrabbits. It overran a whole continent. It caused devastation by burrowing andby devouring the herbage which might have maintained millions of sheep andcattle. Scientists discovered that this particular variety of rabbit (and apparentlyno other animal) was susceptible to a fatal virus disease, myxomatosis. By infectinganimals and letting them loose in the burrows, local epidemics of this diseasecould be created. Later it was found that there was a type of mosquito whichacted as the carrier of this disease and passed it on to the rabbits. So while therest of the world was trying to get rid of mosquitoes, Australia was encouragingthis one. It effectively spread the disease all over the continent and drasticallyreduced the rabbit population. lt later became apparent that rabbits were developinga degree of resistance to this disease, so that the rabbit population wasunlikely to be pletely exterminated. There were hopes, however, that theproblem of the rabbit would bee manageable.Ironically, Europe, which had bequeathed the rabbit as a pest to Australiaacquired this manmade disease as a pestilence. A French physician decided toget rid of the wild rabbits on his own estate and introduced myxomatosis. It didnot, however, remain within the confines of his estate. It spread through Francewhere wild rabbits are not generally regarded as a pest but as a sport and a usefulfood supply, and it spread to Britain where wild rabbits are regarded as a pestbut where domesticated rabbits, equally susceptible to the disease, are the basisof a profitable fur industry. The question became one of whether Man could controlthe disease he had invented.劉曉華 liuxiaohua72@19Lesson 18 PorpoisesThere has long been a superstition among mariners that porpoises will savedrowning men by pushing them to the surface, or protect them from sharks bysurrounding them in defensive formation. Marine Studio biologists have pointedout that, however intelligent they may be, it is probably a mistake to credit dolphinswith any motive of lifesaving. On the occasions when they have pushed toshore an unconscious human being they have much more likely done it out ofcuriosity or for sport,as in riding the bow waves of a ship. In 1928 some porpoiseswere photographed working like beavers to push ashore a waterlogged mattress.If, as has been reported, they have protected humans from sharks, it may havebeen because curiosity attracted them and because the scent of a possible mealattracted the sharks. Porpoises and sharks are natural enemies. It is possiblethat upon such an occasion a battle ensued, with the sharks being driven awayor killed.Whether it be bird, fish or beast, the porpoise is intrigued with anything thatis alive. They are constantly after the turtles, the Ferdinands of marine life, whopeacefully submit to all sorts of indignities. One young calf especially enjoyedraising a turtle to the surface with his snout and then shoving him across thetank like an aquaplane. Almost any day a young porpoise may be seen tryingto turn a 300pound sea turtle over by sticking his snout under the edge of hisshell and pushing up for dear life. This is not easy, and may require two porpoisesworking together. In another game, as the turtle swims across the oceanarium,the first porpoise swoops down from above and butts his shell with his belly.This knocks the turtle down several feet. He no sooner recovers his equilibriumthan the next porpoise es along and hits him another crack. Eventually theturtle has been butted all the way down to the floor of the tank. He is now satisfiedmerely to try to stand up, but as soon as he does so a porpoise knocks himflat. The turtle at last gives up by pulling his feet under his shell and the gameis over.劉曉華 liuxiaohua72@20Lesson 19 The stuff of dreamsIt is fairly clear that the sleeping period must have some function, and becausethere is so much of it the function would seem to be important. Speculationsabout its nature have been going on for literally thousands of years, and one oddfinding that makes the problem puzzling is that it looks very much as if sleepingis not simply a matter of giving the body a rest.39。 Rest 39。, in terms of muscle relaxationand so on, can be achieved by a brief period lying, or even sitting down. Thebody39。s tissues are selfrepairing and selfrestoring to a degree, and function bestwhen more or less continuously active. In fact a basic amount of movement occursduring sleep which is specifically concerned with preventing muscle inactivity.If it is not a question of resting the body, then perhaps it is the brain that needsresting? This might be a plausible hypothesis were it not for two factors. First theelectroencephalograph (which is simply a device for recording the electricalactivity of the brain by attaching electrodes to the scalp) shows that while thereis a change in the pattern of activity during sleep, there is no evidence that thetotal amount of activity is any less. The second factor is more interesting andmore fundamental. In l960 an American psychiatrist named William Dementpublished experiments deal