Rilliet and Barthez undertook to measure the circumference of the heart at the base of the ventricles, with the heart filled and empty, in the cadavers of 193 children 13-hich came to autopsy. These inves tigations are especially valuable because niany of the children died so young. Thus 51 cases were under 24 years; 29 between 3 and 34 years; 21 from 4 to 44 years and 14 from 5 to 54 years; so that 115, out of 193 children, had not yet reached the age of 6 years.
Millet and Barthez came to the following conclusions: 1. The circumference of the heart does not increase relatively with age; it is almost the same from 15 months to 54 years; from then on it increases regularly until puberty.
2. The distance from the base to the apex of the heart, anteriorly, is almost exactly one half of the entire circumference at the base of the ventricles.
3. The greatest thickness of the wall of the right ventricle varies little with regard to age; up to the sixth year it pleasures on the aver age 2 mm., in later 3-ears usually from 2 to 4 min.
4. The greatest thickness of the wall of the left ventricle up to the sixth year is not quite one, later commonly more than one cm.
5. The size of the right venous ostium remains almost the same up to the fifth year; from this time to the tenth year it increases slightly, but only grows somewhat in the tenth year.
6. The left venous ostimn, always smaller than the right, increases a trifle more regularly than the right from year to year.
7. The aortic ostium hardly grows at all from 15 months to 13 years.
S. The pulmonary ostium, on the contrary, grow-s considerably from the sixth to the eighth year, so that, although it was just as large or hardly larger than the aortic ostium before that time, it is much larger than that opening afterward.
Looking back over these conclusions shows that the heart of the young child has great advantages over that of all other ages, especially of later childhood. That the circumference of the heart does not increase through the first five years, although the size and weight of the heart do, shows that the heart muscle steadily becomes builder and stronger during this time. It follow-s from this that the increase in the circum ference of the heart during this time is due, not to increase in the cavity, but to continual increase in the muscle mass. After the end of the first
five years, the increase in the size of the heart is accompanied by con siderable dilatation of its cavities at the same time.
The long time that the size of the ostia remains stationary also speaks in favor of the child's heart and its working ability, which is relatively small in spite of its bulky musculature. This circumstance proves that the obstacles which the cardiac muscle has to overcome, upon the entrance and exit of the blood stream through the ostia, are incom parably slighter in earliest infancy than at more advanced periods of life.
From all of this it results that functional disturbances of the heart muscle occur much less frequently in childhood than in adults, and that injuries of general significance will exert an influence upon the child's heart very much later than upon the heart of an adult man. The child's heart, also, as opposed to pathologic changes in its valvular apparatus, has more material to make up for disturbances in compen sation tlependent upon the performance of its work; i.e., it always has something in reserve.
Blood Pressure.—The blood pressure is best measured by Gart ner's tonometer, provided witb smaller finger compressors and rings, suitable for children. An exact estimation in infants is not always pos sible because of the small size of the finger phalanges, the thick cushion of fat upon them and the difficulty in adapting the rubber compressors. Trumpp found the average estimate in a healthy infant to be 80 min.
The following figures are to be considered normal, according to Kolossowa.
Considerable diminution in blood pressure gives an unfavorable prognosis, especially in diphtheria.
The relative mass of blood in the newborn infant is the same as in the adult (Robin and Hiffelsheim). The work of the beart in the unit of time, taken absolutely, is, according to Vierordt, 20 times as great in the adult as in the newborn infant; relatively, it is greater in the child than in the adult. The mass of blood which, in the unit of time, passes through the unit of weight of the organism is 379 c.c. in the new born infant; 306 c.c. in the child of 3 years; 246 c.c. in one 14 years old, and 206 c.c. in the adult.