^909] CARTER— EVOLUTION OF THE CITY OF ROME. 139 



posedly protected by the city wall. For the worship of Apollo was 

 purely an affair of the Roman state, and hence could well be inside 

 the wall provided it was outside the pomerium. But again under 

 our present supposition we realize that the Aventine also was a 

 suburb and hence, so far as protection was concerned, it would be 

 a matter of indifference whether the temple was on the Aventine 

 or in the Campus INIartius. 



Turning from the field of religion to that of constitutional de- 

 velopment, it has always been difficult to understand why there 

 should have been only four city tribes, named after the four regions, 

 in case the city so soon extended its borders and took in the Aven- 

 tine. But if the Aventine was added two centuries' later it will 

 readily be seen that the force of habit two centuries old caused the 

 number of city tribes to be limited to four even when the city had 

 exceeded the local limits of the four old regions. 



But when we turn to the question of the increase in Rome's 

 population and the disposal of it we have our best argument for 

 treating the Aventine as a suburb. The population was increasing 

 rapidly — we see signs of it in the growing number of foreigners 

 both tradespeople and handicraftsmen. By degrees there arose a 

 problem very similar to that of modern Rome, a dearth of houses for 

 the working classes. It was then (456) that a law was passed pro- 

 viding for the plebeians on the Aventine.^* Had the Aventine been 

 an internal part of the city it is difficult to see why it would not 

 have been occupied long before. But as an extreme measure the 

 expedient of giving the plebeians land in the suburbs might easily 

 have been adopted. 



Thus it was that the city began to outgrow its walls, both in the 

 Aventine region and in the Campus Martins. The proof of this 

 outgrowing is given us in the story of the Gallic catastrophe in 

 B. C. 390. For it is only thus that we can understand why the city 

 was no longer capable of defending itself, and why the Gauls cap- 

 tured it without difficulty, the capitolium alone offering a successful 

 resistance. The tradition of the Gallic catastrophe seems to do 



'' On this law, the lex Icilia, cp. Dionys. 10, 31, and Liv. 3, 31, i. 



