BOOK III.

6 7

However, such a junction of veins sometimes disunites and in thisway it happens that the vein which was the right-hand vein becomesthe left; and again, the one which was on the left becomes the right.

Furthermore, one vein may be split and divided into parts by some hardrock resembling a beak, or stringers in soft rock may sunder the vein andmake two or more. These sometimes join together again and sometimesremain divided.

A, B—Veins dividing. C—The same joining.

Whether a vein is separating from or uniting with another can be deter-mined only from the seams in the rocks. For example, if a principalvein runs from the east to the west, the rock seams descend in depthlikewise from the east toward the west, and the associated vein whichjoins with the principal vein, whether it runs from the south or the north,has its rock seams extending in the same way as its own, and they do notconform with the seams in the rock of the principal vein—which remainthe same after the junction—unless the associated vein proceeds in the samedirection as the principal vein. In that case we name the broader vein theprincipal one, and the narrower the associated vein. But if the principalvein splits, the rock seams which belong respectively to the parts, keepthe same course when descending in depth as those of the principal vein.

But enough of venae profundae, their junctions and divisions. Nowwe come to venae dilatatae. A vena dilatata may either cross a vena profunda,or join with it, or it may be cut by a vena profunda, and be divided into parts.