Custom, grown out of traditional experience of what a single herdsman and his dog could manage, had determined, it seems, the size of the normal herd. Thus in the Gwentian Code[39] we are told that ‘a legal herd of cattle is 24 kine.’ And custom tenaciously adhered to tribal rules in such matters. Thus in the Denbigh Extent it is mentioned that the whole villata of Arquedelok was _in manu domini_ by reason of escheats and exchanges, and that a portion of it was let _ad firmam_ to nine firmarii, each of whom held for a term of years 31 acres, with one bull and 24 cows, paying per annum 73_s._ 4_d._, and rendering to the lord at the end of his term the said bull and cows or their price, together with the land and a house built thereon.[40] Here, even in a case in which Henry de Lacy was introducing into Wales holdings and herds in severalty, and very possibly introducing English tenants, he adhered to the Welsh tribal rule of the one bull and 24 cows to the herd. So also in the survey of St. David’s, under the head _Glaston_ in Breconshire, the number 24 of _grossa animalia_ is spoken of as the usual number _ab antiqua consuetudine_, and in the arrangement of common pasture one great animal is said to count as equal to twelve sheep. The normal herd of the trefgordd was then 24 cows, or their equivalent in bullocks and sheep. During the summer months the herdsman living out on the mountains was responsible with his dog for the cattle of the trefgordd. And his dog was worth as much as a cow or an ox, if it was one that ‘will go _before_ the herd in the morning and _behind_ them in the evening, and make three turns _round_ them in the night.’[41] Having no cattle of his own in the herd, the herdsman’s testimony as to whose cattle were injured, and as to whose cattle had done the injury, was held, when such cases arose, to be sufficient to make the owner responsible, while as regards injuries done by the cattle of one trefgordd to those of another there was joint responsibility.[42] There is common sense in such rules to begin with, and then, having grown into custom, they become perpetuated when custom is codified. [Sidenote: The common churn.] The trefgordd possessed further a common churn. This implies that the milk of the cows was thrown altogether into this one churn as in Swiss mountain communes now. One of the dues from a taeog trev, _i.e._ a group of _non_-tribesmen, was a cheese made from a day’s milking of all the cows in the herd. So that we note in passing that the taeog-tref, _i.e._ of non-tribesmen, also had its herd and was in fact a trefgordd.[43]