15. Dry weather is injurious to other testacea, for it renders them fewer in quantity and inferior in quality, and the pectens become more red. In the Pyrrhæan Euripus the pectens perish, not only from the instrument with which the fishermen scrape them together, but also from dry weather. The other testacea thrive in wet weather, because it makes the sea-water fresher. The cold of the Pontus and of the rivers that flow into it renders bivalve shells rare. The univalves, however, are frozen in cold weather. This is the nature of aquatic animals. CHAPTER XXI. 1. Among quadrupeds, swine suffer from three diseases, one of these is called sore throat, in which the parts above the jaws and the branchia become inflamed; it may also occur in other parts of the body, and frequently seizes upon the foot, and sometimes the ear. The neighbouring parts then become putrid, until it reaches the lungs, when the animal dies; the disease spreads rapidly, and the animal eats nothing from the period of the commencement of the disease, be it where it will. The swineherds have no other remedy but the excision of the part before the disease has spread far. 2. There are two other diseases which are both called craura. One of them consists in a pain and weight in the head, with which many of them are afflicted; the other is an excessive alvine discharge. This appears to be incurable. They relieve the former by the application of wine to the nostrils, and washing them with wine. Recovery from this disease is difficult, for it generally carries them off on the third or fourth day. 3. They suffer particularly from sore throat, when the summer bears abundantly, and they are fat. The fruit of the mulberry is good for them, and abundant washings with warm water, and scarification beneath the tongue. If the flesh of swine is soft, it is full of small lumps (chalazæ) about the legs, neck, and shoulders; for in these parts the chalazæ are most frequent. If there are but a few, the flesh is sweet; if many, it becomes very fluid and soft.