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Everyone knows that nowadays artificial insemination is used to breed everything from cattle and horses to rhinos, gorillas, and humans. I know how they get sperm from humans, but how do they get it from bulls and male gorillas? Do they show them dirty heifer pictures? Gorilla porn? Do they use blow-up female rhino dolls? The mind boggles. --S.J. Cowdery, Dallas

Go boggle on your own time, pal. In keeping with the Straight Dope tradition of brutal frankness, however, I may as well tell you that perhaps the most common method of sperm collection involves an artificial vagina. I had thought to edify the Teeming Millions with a do-it-yourself version of this technique taken from an animal breeding manual, but on second thought it's too icky for words. Suffice it to say it involves a 2 3/4-inch automobile radiator hose 18 inches long, a 30-by-3-inch automobile inner tube, and a family-size bottle of Vaseline. An entirely different method, it says here, is "rectal massage of the ampulla." They even show pictures, for Chrissake. Just be thankful I'm doing this job and not you.

What are those antennae you see that have a triangular platform on top of a fifty-foot pole with two or three little antennae sticking up or down on the corners? --Mark Downing, Dallas

They're for cellular telephones, the ultimate (for now) yuppie plaything. The genius of cellular, of course, is that you can divide any region into an increasingly large number of progressively smaller "cells" (the area served by a single antenna) as the number and density (no offense) of mobile-phone users increases. So the cellular antenna will ultimately become as common a feature of the urban landscape as the dandelion, and about as attractive.

THE 200-MPG CARBURETOR REVISITED

You blew it on the question of whether there really are super-high-mileage carburetors [March 17]. High-mileage carbs are based on a simple principle. Detroit carbs put gas in the engine by spraying it in; much of the gas goes into the cylinder still in droplets and burns incompletely. High-mileage "vapor" carburetors pre-warm the gas using exhaust heat pumped through an in-line chamber. This enables the gas to evaporate quickly but thoroughly. More gas is burned and less goes out the tailpipe as pollution. Detroit seems to avoid these designs because they cost more. (Remember saving five cents per Pinto?) But better carbs are out there for the tinkering. --Fred Baube, Washington, D.C.

I got a lot of mail on this, including a report that supposedly originated with the Carb Research Center of Oklahoma, which promotes vapor carbs. The report makes the astonishing claim that theoretical maximum fuel efficiency for a conventional auto is nearly 2,900 mpg. It goes on to tell the story of the original 200-mpg vapor carb, invented in the mid-1930s by one Charles N. Pogue. Another reader says vapor carbs work but they have a big drawback: backfiring.

While I don't want to belittle blue-collar ingenuity, the vapor carb's inventors are trying to solve a nonexistent problem. According to John Heywood, a professor of mechanical engineering at MIT and an authority on internal-combustion engines, incomplete burning of fuel is insignificant in modern cars. Fuel combustion today typically exceeds 97 percent. While it's true cars aren't very efficient--only 20-35 percent of the fuel energy is converted to useful work--that's mostly due to heat loss (through the engine block, out the exhaust pipe) and unavoidable energy loss during burning itself.

The theoretical (and unobtainable) maximum efficiency for a small car like a Honda Civic is around 200 mpg; for your big beaters it's much lower. Claims to the contrary are fraudulent, and I gather Professor Heywood said as much in a report he wrote for the Postal Service, which was investigating high-mileage carb vendors for fraud.

Carburetors in general are an obsolete technology now being replaced by electronic fuel injection, which offers superior emission control. Truth is, vapor carbs are the equivalent of the improved buggy whip. Forget 'em.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.

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