By placing the hand, upon the surface of the body we can readily detect marked variations in the temperature; thus the nose and extremities feel cold in diseases associated with depression of the vital forces, and the palms of the hands and back of the head feel hot in those attended by fever. But the only possible means of detecting slight variations or of obtaining reliable information concerning normal or abnormal body-heat is by the employment of an accurate thermometer. Clinical thermometers, as these instruments are called, are made entirely of glass, and are usually furnished in the shape seen in Fig. 4.

Fig. 4. - Clinical Thermometer.

This instrument is graduated according to the Fahrenheit scale and provided with a self-registering index, which is simply a short column of mercury separated from that in the bulb of the thermometer.

Temperature is usually taken in the rectum of the infant or young child, and in the mouth of a child old enough to understand the purpose of the procedure, and to obey directions to keep the lips closed, the tongue over the bulb of the instrument, and to avoid breaking the glass by the forcible closing of the teeth.

Supposing the rectum be chosen as the place of observation, it is first necessary to be sure that this portion of the gut is free from faeces. The upper end of the stem of the thermometer is then held between the thumb and finger, and the index, by a few vigorous shaking movements, is forced down so far that its upper extremity will be well below the normal mark, to 95 for instance; next, the bulb is covered with sweet oil or vaseline and gently inserted through the anus into the rectum for a sufficient distance to conceal completely the mercury. Here it is allowed to remain, according to the sensitiveness of the instrument, from one-half to two or even five minutes by the watch, and on being removed the degree of temperature is read from the top of the index. The position of the patient in the meanwhile is upon the back, on the nurse's lap, with the legs elevated and controlled by her left hand, the right hand being used in steadying the thermometer.

When taking the temperature in the mouth direct the child to lie down on his back and instruct him not to bite upon the delicate glass. Then, having seen that the instrument is thoroughly clean and that the top of the index is below the normal point, insert the bulb, crosswise, beneath the tongue. The teeth must be lightly closed so as to hold it in position, and the lips closely shut about its stem. For the time necessary to complete the observation breathing must be performed entirely through the nose.

Temperature is also taken in the arm-pit and groin, but the observation in these positions is inaccurate and unreliable.

One more fact is important, namely, that a simultaneous observation in the different positions mentioned will not furnish identical results; the rectal and oral temperature being, normally, at least 1o higher than that of the arm-pit, and 1.50 higher than that of the groin in the same individual.

When properly used the thermometer is of great value in the nursery. At the same time, under opposite conditions, it may be the source of much unnecessary alarm to overanxious parents. To prevent the latter misfortune, all who intend to use the instrument should be familiar with the healthy range of temperature and some of the characteristic variations in disease.

During the first week of healthy life the temperature fluctuates considerably. After this the puerile norm - 98.5 to 99°F. - is established, but until the fourth or fifth month it is greatly influenced by physiological causes of variation, the fluctuations ranging between .9° and 3.6°. By the fifth month regular morning and evening oscillations begin to be noticeable, and certain definite laws are followed. Thus there is a fall in the evening of 1° or 20. The greatest fall occurs between 7 and 9 p. M., and the minimum is reached at, or before, 2 A. M. After 2 a. m. there is a gradual rise, the maximum being reached between 8 and to a. m. Throughout the day the oscillation is trifling. These variations are independent of eating and sleeping.

It may be taken for granted, therefore, that a temperature between 98 and 99 in the morning and 97.5°F and 98.5°F in the evening is the range to be expected in a healthy child beyond the age of five months.

Examples of Variations in Disease. - In disease there may be either a rise above or a fall below the normal standard.

Fever is always associated with an elevation. Rapid and transient rises attend slight catarrhs and passing indigestions. Prolonged rises indicate inflammatory and essential fevers, for example, typhoid, scarlet fever and measles.

The degree of elevation marks the type of the fever. This is moderate when the mercury stands at 102°, severe at 104° or 105°, and very grave above 107°. It is known, however, that infants are extremely sensitive to conditions productive of fever, and that, in them, the temperature, like the pulse, is easily influenced by slight and transient causes: therefore, a high degree of temperature, 104°-105°, in young children is less alarming than in adults, and of less import than a continuance of the elevation, in estimating the gravity of a fever. The duration of the elevation and the peculiar range of the oscillations (for there are oscillations in disease as well as in health) determine the nature of the fever. The febrile oscillations differ from the healthy, in that the lowest marking is noticed in the morning, the highest in the evening.

Variations in the typical range of any given fever are important prognostic omens: a sudden fall of the temperature, together with improvement in the general symptoms, indicates the beginning of convalescence; a similar fall, with an increase of the general symptoms, is a precursor of death. When the morning temperature is equal to that of the preceding evening, there is great danger; if higher, greater danger still. Marked remission in continued fevers is generally a forerunner of convalescence.

Abnormal depression of temperature is occasioned by hemorrhage and by the loss of fluids in cholera infantum or entero-colitis. It is also met with in anaemia, in wasting from insufficient nourishment, in diseases of the heart and lungs attended by imperfect oxidation of the blood, and it constantly attends collapse and the death agony. A maintained temperature of 97° is dangerous in children, and for every degree of reduction below this the risk for life is more than proportionately increased.