It’s partly a question of taste. When Anna Eliza Bray was collecting materials for The Mountains and Lakes of Switzerland (1841) she was proudly shown the ornamented skeleton of St Alexander at Freiburg. ‘Never before had we witnessed any sight so disgusting,’ she recalled. ‘I involuntarily started in horror.’ Any idea of venerating human remains was bad enough for a properly brought-up Anglican, but the mouldering bones bedecked with jewels and embroidered with gold proved viscerally repulsive.

This must be a common reaction to the photographs in a new book, Heavenly Bodies. Skeletons from Roman catacombs, mistaken for the remains of martyrs, were imported by the dozen for churches in Switzerland, Bavaria and Austria, mostly in the 17th and 18th centuries.

They were articulated in suitable poses (like squirrels in a Victorian taxidermy tableau), clad in gems and displayed in glazed niches for popular devotion. At first they seem deliberately grotesque, a memento mori. But the author, Paul Koudounaris, insists that on the contrary, the intention was to give them the highest dignity by ornamenting them with gems mentioned in the Book of Revelation’s description of the heavenly Jerusalem.

If there’s a problem, it’s a cultural (Germanic) thing. Think of Gunther von Hagens and his exhibitions of anatomised bodies. With the catacomb saints, eyes are the most troublesome parts. Hollow orbits are bad enough, but blue gem eyes are worse, reminding us of the ventriloquist’s dummy. Shakespeare’s feelings (‘Those are pearls that were his eyes’) seem closer to the relic-collectors’ than to our own. At Roggenburg in Bavaria the four saints on display have papier-mâché masks, but a hole where a nose should be still makes St Severina behind her veil look like Michael Jackson.

In the centuries after the discovery of the Coemeterium Jordanorum on the via Salaria, Rome, in 1578, such skeletons were carted over the Alps to be adorned by craftswomen such as Potentiana Hammerl, a nun from Freising (where Pope Benedict XVI more recently lived). She set the skull, ribcage and limbs of St Albert with red and blue gems and bound his bones with pearls.

One Swiss Guard at the Vatican, Capt Johann Pfyffer, dispatched 25 catacomb saints to his native land in the 17th century. These had not been sold (that would have been the mortal sin of simony), but transport did not come cheap, even if some pious innkeepers en route assigned the skeletons rooms of their own free of charge. Since the names of the dead seldom survived in the catacomb niches, they were given generic new names: Felix (Happy), Constantius (Constant) or even Incognitus (Unknown).

Martyrs’ relics were used as a sort of conduit for prayers, who asked their intercession for those still on earth. The theory seemed reasonable to believers such as St Jerome, who wrote that such ‘venerable bones are held to be the altar of Christ’. He opposed the scoffing second-century Celsus, who declared, ‘Corpses should be disposed of like dung, for they are dung.’ Today our sensibility is more likely to be that of Celsus. Corpses, while deserving of respect, fall definitely in the category of unclean things.

So in Porrentruy, Switzerland, the catacomb-saint Faustine now lies in a lumber room. Yet in the village of Rottenbuch, Bavaria, whose citizens wept in 1803 as the secular magistrate auctioned off their beloved saints Primus and Felicianus, good fortune and fund­raising brought them back in 1977 to be honoured again in all their ghastly glory.

Christopher Howse/The Telegraph