DO YOU REMEMBER the good old days of civil defense? The sinking of fallout shelters in suburban backyards? The helpful feature stories on how to decorate your shelter and make it an attractive, fun place? The gripping philosophical debate over whether it might not be both practical and justifiable to have a shotgun on hand to kill anyone who tried to intrude into your special space? Ah, those were the days. But don't despair - if your friendly House of Representatives has anything to do with it, they may come back. For Monday, the House, in its wisdom, authorized the administration to spend $44.8 million more on civil defense in fiscal 1978 than the Pentagon had even asked for. The total sum, $134.8 million, would amount to the nation's biggest civil-defense expenditure in well over a decade.

The brief debate on the House floor was wonderful. There is no other way to describe the manner in which the advocates of civil defense discussed - in Rep. G. William Whitehurst's words - the prospective effects of "the nuclear cookout, as sometimes it is called." The nuclear cookout? Well, no one exactly argued that nuclear war would be just one prolonged marshmallow roast, but it certainly was argued that nuclear war was much more manageable than a lot of nervous Nellies among us seem to think. Mr Whitehurst himself cited a report prepared by the Boeing Aerospace Company, which cheerfully observed that "the day after the explosion, bridges into downtown Hiroshima were open to traffic, and electric service was restored in some areas." How about that, sports fans?

Naturally, Mr. Whitehurst and his like-minded House colleagues did not think that the Hiroshima model, encouraging as it was, was good enough.For which reason they support the extra funds for building fallout shelters. And according to testimony they took in committee and in which they have positively touching faith, it seems that such shelters can actually be of great help to our big cities when push comes to cookout. As Mr. Whitehurst put it: "We were told . . . if we had an adequate shelter program for people to be able to walk to and within walking distance of about a day of our major urban areas that we could hold the casualties down."

The idea of a day's walking distance, Mr. Whitehurst explained, was based on "a three-day notice of nuclear attack." We were wondering whether there might be something in the bill that required the Russians to give three days' notice - and perhaps also file an environmental impact statement - before launching a nuclear attack.But it turned out that the three days had merely been borrowed by Mr. Whitehurst from the Russians, whose own civil defense, he said, was based on the three-day rule.

In fact the whole thing is a preposterous mirror-image play with the Russians whose own civil defense effort the members of the House are trying to ape. Never mind that that effort makes little sense and that its principal effect is merely to suggest to people in this country that the Soviets are planning nuclear war, a suggestion that logically leads to more weapons production over here. Defense Secretary Harold Brown has recently put it exactly right: "Should they continue to build up their civil defense activity, we would probably have to take some action to assure that our strategic forces were augmented or that their targeting was changed . . . ." In other words, civil defense against nuclear war is a mugs' game; the offense can overcome it. With luck the members of the Senate will keep that in mind when the House handiwork comes before them.