But I am digressing from my subject. Another step of the religious and material transformation of the city is marked by the substitution of chapels and shrines for the old _aræ compitales_, at the crossings of the main thoroughfares. The institution of altars in honor of the _Lares_, or guardian genii of each ward or quarter, is ancient, and can be traced to prehistoric times. When Servius Tullius enclosed the city with his walls, there were twenty-four such altars, called _sacraria Argeorum_. Two facts speak in favor of their remote antiquity. The priestess of Jupiter was not allowed to sacrifice on them, unless in a savage attire, with hair unkempt and untrimmed. On the 17th of May, the Vestals used to throw into the Tiber, from the Sublician bridge, manikins of wickerwork, in commemoration of the human sacrifices once performed on the same altars. When Augustus reorganized the capital and its wards, in the year 7 B. C., the number of street-shrines had grown to more than two hundred. Two hundred and sixty-five were registered, A. D. 73, in the census of Vespasian; three hundred and twenty-four at the time of Constantine. A man of much leisure, and evidently of no occupation, the cavaliere Alessandro Rufini, numbered and described the shrines and images which lined the streets of Rome in the year 1853. As modern civilization and indifference will soon obliterate this historical feature of the city, I quote some results of Rufini's investigations.[24] There were 1,421 images of the Madonna, 1,318 images of saints, ornamented with 1,928 precious objects, and 110 ex-votos; 1,067 lamps were kept burning day and night before them,--a most useful institution in a city whose streets have not been regularly lighted until recent years. [Illustration: The Shrine and Altar of Mercurius Sobrius.] As prototypes of a classical and Christian street-shrine, respectively, we may take the _ædicula compitalis_ of Mercurius Sobrius, discovered in April, 1888, near S. Martino ai Monti, and the _immagine di Ponte_, at the corner of the Via dei Coronari and the Vicolo del Micio. The shrine of Mercury near S. Martino was dedicated by Augustus, in the year 10 B. C. The inscription engraved on the front of the altar says: "The emperor Augustus dedicated this shrine to Mercury in the year of the City, 744, from money received as a new-year's gift, during his absence from Rome."