Aug. 21, 1961 - In the first 6 months of this year, 1,171 New York City policemen were attacked while trying to make arrests. From July 1 through August 14, these assaults increased in incidence and viciousness. In that 45-day period, 133 policemen were injured - almost double the 69 hurt during the corresponding period in 1960. What the police cannot understand is why, when they corner three teenaged boys carrying loaded shotguns - as two patrolmen did on Aug. 14 in the Bronx - more than 100 youths and adults gather to jeer them and throw beer cans and rocks from roofs and the street. One retired detective said he did not think the problem was primarily racial. "The Irish gangs were the big problem when I was a young cop," he said, "but we generally had it out with fists or clubs. Now you get a knife or a zip-gun slug in the belly. But I think it will pass. They'll quiet down just like the Irish and the Italians and the Poles did. A better job, a better house, more money calms a fellow down."