This instrument is employed for taking the internal temperature of the body, which is most conveniently done by placing the instrument for about three minutes in the animal’s rectum. Owing to the almost general adoption of this method, the expression “internal temperature” is used as a rule to signify “rectal temperature”; although the respective temperatures of different parts of the body vary to a slight extent. The practice of placing the thermometer in the mouth, as is the custom in human medicine, is not suitable to animals, owing to the danger of the patient breaking the glass instrument with the teeth. The indications afforded by the clinical thermometer are valuable guides as to the state of the animal’s health at the time, or what it will shortly be. Thus, in a horse at rest under ordinary conditions, if there be a rise of three or four degrees without the animal evincing any other sign of illness, we may be assured that disease in some form will, after a day or two, manifest itself in him. During illness, a temperature of, say, 106° F. or more points to a condition of great danger. The clinical thermometer is especially useful in indicating the state of an animal during infective diseases and diseases of the organs of breathing. A fall in temperature, when it has been abnormally high, will generally point to a favorable termination of the disease; although in some cases it is the precursor of rapidly approaching death. TEMPERATURE DURING HEALTH. As a rule, there is a daily variation in the internal temperature of a healthy animal of about 1° F.; the maximum being attained at about 6 o’clock in the evening. In the adult animal, the temperature is about 1° F. higher than in a very young or very old animal. It is about 1° F. less in the female than in the male, except when she is “in season,” during which time it is about 2° F. higher than normal. The temperature of well-bred animals is higher than that of common animals. A rise of 4° or 5° F., compatible with health, may be observed in animals during violent exercise or work in hot weather. The temperature of well-fed animals is higher than that of poorly-fed ones. During digestion, it rises about 1° F., and falls about the same amount during sleep. Exposure to the rays of a hot sun for a few hours may cause a rise of as much as 3° F., and the effects of cold and rain may equally lower it. NORMAL TEMPERATURE OF THE HORSE.— From 2 to 5 years old the temperature is 100.6° F. From 5 to 10 years old the temperature is 100.4° F. From 10 to 15 years old the temperature is 100° F. From 15 to 20 years old the temperature is 98.4° to 100.2° F. New born foals’ temperature will run from 102° to 104° F. TEMPERATURE OF CATTLE.—Normal temperature is from 101.8° to 102° F. Compared with the horse, the daily variations are small.