问答题

The years between 1870 and 1895 brought enormous changes to the theater in the United States as the resident company was undermined by touring groups, as New York became the only major Center of production, and as the long run replaced the repertory (库存) system. By 1870, the resident stock company was at the peak of its development in the United States. The 50 permanent companies of 1870, however, had dwindled to 20 by 1878, to 8 by 1880, to 4 by 1887, and had almost disappeared by 1900.
While the causes of this change are numerous, probably the most important was the rise of the "combination" company (that is, one that travels with stars and full company): Sending out a complete production was merely a logical extension of touring by stars. By the 1840’s many major actors were already taking along a small group of lesser players, for they could not be sure that local companies could supply adequate support in secondary roles.
There is much disagreement about the origin of the combination company. Bouciault claimed to have initiated it around 1860 when he sent out a troupe with Colleen Bawn, but a book published in 1859 speaks of combination companies as already established. Joseph Jefferson HI also declared that he was a pioneer in the movement. In actuality, the practice probably began tentatively during the 1850’s, only to be interrupted by the Civil War. It mushroomed in the 1870’s, as the rapid expansion of the railway system made it increasingly feasible to transport full productions. In 1872, Lawrence Barrett took his company, but no scenery, on tour; in 1876, Rose Michel was sent out with full company, scenery, and properties. By the season of 1876～1877 there were nearly 100 combination companies on the road, and by 1886 there were 282.

According to the passage, the development of full touring companies was aided by ______.