The animal must be properly confined for the operation. Heifers are usually held in the standing position by fastening the head securely, and crowding the left side of the animal against a solid board partition, or side of a chute. If the vaginal operation is performed, the mare or cow may be confined in stocks. The bitch is usually anesthetized and placed on her back on a table that is inclined, so that the hind parts are elevated. Ovariotomy cannot be successfully performed by an untrained and inexperienced operator. The necessary precautions against the infection of the part must be observed, in order to promote the healing of the wound and prevent peritonitis. The seat of the operation should be carefully cleaned and disinfected. _Following the operation_ the animal should be fed a spare diet for a few days. This is a very necessary part of the care of the bitch. The general condition of the animal should be noted daily until there is no further danger from wound infection. Healing is usually completed in from seven to twelve days. The sutures should then be removed, and if stitch abscesses occur, the part should be washed with a disinfectant. QUESTIONS 1. What is the purpose of dehorning cattle? Give different methods of removing the horns. 2. Give the causes and treatment of choking. 3. What is the purpose of castration and ovariotomy? 4. At what age is it best to practise castration and ovariotomy? 5. In what way should an animal be prepared for castration? Give a description of the method of castration in the different animals. 6. What special care should be given following castration? 7. What are some of the complications that may follow castration? PART V.--PARASITIC DISEASES CHAPTER XXIV PARASITIC INSECTS AND MITES Parasitic insects are common causes of skin diseases in domestic animals. The diseased conditions of the skin, and the irritation that they may cause the animal, depend on the life history and habits of the parasite. Species that are unable to live independently of a host and are permanent parasites are usually the most injurious to the animal. This is especially true of parasites that are capable of puncturing the skin or burrowing into it. Temporary parasites may cause fatal forms of disease. This is true of the larva? of the sheep bot-fly, which develop in the sinuses of the head, causing severe inflammation of these parts, nervous symptoms and death. The character of the symptoms of a parasitic disease depends on the habits of the parasite, and the tissue or organ, that it may attack. The parasitic flies belong to the order _Diptera_, and the families _Muscidae_ and _OEstridae_. Fleas belong to the sub-order _Pulicidae_. The order _Hemiptera_ includes the lice, and the most important families are _Pediculidae_ and _Ricinidae_. Mites and ticks belong to the order _Acarina_. The most important parasites belonging to this order are the _Sarcoptidae_ and _Ixodidae_.