very frequent also in the vine,' which shows that he made no
distinction between milky juice and the exuding water of the
weeping vine-stock. These narrow veins cannot be seen on
account of their fineness; but in every stem and in every root
things may be discerned which like nerves in animals can be
split longitudinally and are called the nerves of the plant, or
also certain thicker things, such as those which branch in
most leaves and are there called veins. These should be
considered as food-passages and as answering to the veins
in animals; but plants have no main vein like the vena
cava in animals, but many fine veins pass from the root to the heart of the plant (cor, root-neck, see above, Book I. chap. 2), and ascend from it into the stem; for it was not necessary that the food should be collected in a common
receptacle in plants, as it is in the heart in animals, where this
is necessary for the production of the spiritus, but it was
sufficient that the fluid in plants should be changed by contact
with the medulla cordis (in the root-neck), as it is changed
in animals in the marrow of the brain or in the liver ; and in
these organs the veins are very narrow, as they are in plants.
Since plants have no sense-perception, they cannot seek their food like animals, but they draw up the moisture from the ground into themselves in a way of their own ; but it is not easy to see how this takes place. Cesalpino, in trying to explain this, gives us a glimpse into the physics of the day, and we observe also to our surprise an attempt made to explain phenomena in living creatures by physical laws, a step beyond the limits of Aristotelian modes of thought and in the right direction. It is not the ratio similitudinis, which draws iron to the magnet, that can cause the attraction of the juice by the roots, for then the smaller would be drawn to the larger ; and if the attraction of the fluid of the earth by the roots were the same thing as the attraction of the iron by the magnet, the moisture of the earth would draw out the juice from the plant, which is just what does not happen. Nor can
