452 Theory of the Nutrition [BOOK in. 



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 



