4. The fat around the pupil of the eye is common to all animals; for all have fat in this part, that possess it, and are not hard-eyed. Fat animals, both male and female, are more inclined to be barren, and all old animals become fat more readily than young ones, especially when they increase in depth, having obtained their proper width and length. CHAPTER XIV. 1. The following is the nature of the blood. This is most essential and common to all sanguineous animals, and is not superadded, but exists in all animals that are not in a perishing condition. All the blood is in a vessel called the veins, but in no other part of the body, except the heart. The blood of all animals has no sense of touch, nor has the excrementitious matter in the stomach; neither have the brain, nor the marrow, any sensation of touch; but wherever the flesh is divided, the blood flows in the living subject, unless the flesh is perishing. It is the nature of the blood to have a sweet juice, as long as it is healthy and a red colour, and that is bad which either by nature or disease is black. The best kind of blood is neither very thick nor thin, unless it is vitiated either by nature or disease. 2. In living animals it is always warm and moist, but when taken out of the animal the blood of all creatures coagulates, except that of the stag and deer, and perhaps some others of the same nature. The blood of all other creatures coagulates, unless the fibre is taken out of it. Bullock's blood coagulates faster than that of any other animals. Amongst sanguineous animals, those which are both internally and externally viviparous, have the most blood, and after them the oviparous sanguineous animals; those which are well disposed, either by nature or by health, have not a great deal of blood, as in those that have just drank; nor a very little, as in those which are very fat. Fat animals have pure blood, though the quantity is small; as they become more fat they lose a portion of their blood, for fat is free from blood. Fat is not corruptible, but blood and the parts that contain blood are very corruptible; of these the parts surrounding the bones are most corruptible.