"Although the timing of the offerings can be pinned to a traditional rural agricultural calendar, it is important to remember that these sorts of offerings can in fact address very contemporary urban and rural concerns," says Andrew Orta, an anthropologist at the University of Illinois, who specialises in the Bolivian highlands.

Beyond the yatiris and the hawking cries of the saleswomen, the market points to a thriving urban culture. Next to a stall selling fox and mountain lion hides and another specialising in pig foetuses, Miguel Miranda blares the rap music of Rimadores Locos, an El Alto-based band that performs in a hybrid of Aymara and Spanish.

"August is also my best month to sell CDs," says Mr Miranda, 25, in front of his music booth.

"Someone walks by looking for a llama foetus, or maybe the hide of a skunk, but if they're young they might want a little music as well."

Once the requisite ingredients are sold by vendors in the witch's market, the yatiris gather them into what they call a misa. The word is the same as the Spanish term for Mass, but linguists say it also may be an Aymarisation of another Spanish word, mesa, or table.

The yatiris set the misa on coals, and along Avenida Panoramica, and in the maze of side streets, smoke from the offerings mixes with the smell of sewage seeping into the bare ground. The yatiris toss pure alcohol or beer on the small pyres, causing flames to leap in the cold air. Once the items are consumed by fire, the yatiris generally bury the remains, thus feeding the earth as springtime - or what passes for springtime on these frigid high plains - approaches.

Reflecting a fusion of rural and urban customs, the customers for these offerings aspire to a variety of hopes, from abundant crops, success in studies, an accident-free year for truck drivers or vibrant sales for the local industrial factories or textile manufacturers.

A sign on the door of the small shack of yatiri Jorge Sharo sums it up: "For love, travel, marriage, health, legal problems, making lost things appear, duty inspections, exams at the teacher's college."

The recipes for good fortune are equally broad. A deer foetus offers luck for tin miners who descend into the bellies of mountains. For a love triangle, the yatiris recommend the foetuses of a dog and cat, the idea being that an illicit affair can come undone if the lovers fight like cats and dogs.

Then there are the items employed to address financial concerns.

"The rich guys from La Paz drive up here for the vicuna foetus," says one saleswoman, Nina Quispe, 28, referring to an endangered animal, related to the llama and alpaca and usually banned from the relatively sanitised witch's market in La Paz. A vicuna foetus is the most expensive misa item - it costs 800 bolivianos, about $140.

Functioning as a kind of twin city to La Paz below it, El Alto was settled by veterans of the bloody Chaco War of the 1930s and, in the 1980s, by miners expelled from their jobs.

Immigrants from throughout the highlands poured in, expanding its network of cinderblock and adobe hovels. Political activism became fused into El Alto's identity.

By blockading roads and sealing off the nearby international airport "protesters from El Alto were able to besiege La Paz," says Sian Lazar, author of El Alto, Rebel City , a book on the city's political power.

Evo Morales, a former llama herder who rose to the presidency thanks in part to the support of El Alto's protesters, sometimes has yatiris in his entourage.

But even Bolivia's politics were eclipsed at the market. "I'm looking for something that will help a countryman on a voyage of emigration," says Fernando Sinani, 34. "What do you need for someone who is about to set out across the sea?"