We have considered till now the different aspects assumed by common of pasture, when it arises within the manor, and as a consequence of the arrangement of its holdings. But this is not the only way in which common of pasture may arise. It may originate in an express and special grant by the lord either to a tenant or to a stranger[542]; it may also proceed from continuous use from time beyond legal memory[543]: it must have been difficult in many cases to prevent strangers from establishing such a claim by reason of long occupation in some part of a widely stretching moor or wood pasture[544]. It was not less difficult in such cases to draw exact boundaries between adjoining communities, and we find that large tracts of country are used as a common pasture-ground by two villages, and even by more[545]. Neighbours deem it often advantageous to establish a certain reciprocity in this respect[546]. By special agreement or by tacit allowance lords and tenants intercommon on each other's lands: this practice extends mostly to the waste only, but in some cases the arable and meadow are included after the removal of the crop and of the hay. The procedure of the writ 'quo jure' was partly directed to regulate these rights and to prevent people from encroaching wantonly upon their neighbours[547]. When land held in one fee or one manor was broken up for some reason into smaller units, the rights of pasture were commonly kept up according to the old arrangements[548]. These different modes of treating the pasture present rather an incongruous medley, and may be classified in several ways and deduced from divers sources. [Modern classification of commons.]