municate by a transverse duct, which ultimately becomes the left innominate vein. The left canal of Cuvier atrophies and becomes a fibrous cord. A transverse branch now appears, which carries the blood from the left cardiac vein into the right, and becomes the vena azygos minor; the right cardinal vein becomes the vena azygos major.

Circulation of Blood in the Fetus.-The blood returning from the placenta, after having received oxygen, and being freed from carbonic acid, is carried by the umbilical vein to the under surface of the liver; here a portion of it passes through the ductus venosus into the ascending vena cava, while the remainder flows through the liver and passes into the vena cava by the hepatic veins. When the blood is emptied into the right auricle, it is directed by the Eustachian valve through the foramen ovale, into the left auricle, thence into the left ventricle, and so into the aorta to all parts of the system. The venous blood returning from the head and upper extremities is emptied, by the superior vena cava, into the right auricle, from which it passes into the right ventricle, and thence into the pulmonary artery. Owing to the condition of the lung, only a small portion flows through the pulmonary capillaries, the greater part passing through the ductus arteriosus, which opens into the aorta at a point below the origin of the carotid and subclavian arteries. The mixed blood now passes down the aorta, to supply the lower extremities, but a portion of it is directed, by the hypogastric arteries, to the placenta, to be again oxygenated.

At birth, the placental circulation gives way to the circulation of the adult. As soon as the child begins to breathe, the lungs expand, blood flows freely through the pulmonary capillaries, and the ductus arteriosus begins to contract. The foramen ovale closes about the tenth day. The umbilical vein, the ductus venosus, and the hypogastric arteries become impervious in several days, and ultimately form rounded cords.

TABLE OF PHYSIOLOGICAL CONSTANTS.

Mean height of male, 5 feet 61⁄2 inches; of female, 5 feet 2 inches.
Mean weight of male, 145 pounds; of female, 121 pounds.
Number of chemical elements in the human body; from 16 to 18.
Number of proximate principles in the human body; about 100.
Amount of water in the body weighing 145 pounds; 108 pounds.
Amount of solids in the body weighing 145 pounds; 36 pounds.

Amount of food required daily; 16 ounces meat, 10 ounces of bread, 31⁄2

ounces of fat, 52 ounces of water.

Amount of saliva secreted in 24 hours; about 31⁄2 pounds.

Function of saliva; converts starch into glucose.

Active principle of saliva; ptyalin.

Amount of gastric juice secreted in 24 hours; from 8 to 14 pounds.
Functions of gastric juice; converts albumin into albuminose.

Active principles of gastric juice; pepsin and hydrochloric acid. Duration of digestion; from 3 to 5 hours.

Amount of intestinal juice secreted in 24 hours; about I pound.

Function of intestinal juice; converts starch into glucose. Amount of pancreatic juice secreted in 24 hours; about 11⁄2 pounds. Active principles of pancreatic juice; trypsin, amylopsin, and steapsin.

Functions:

I. Emulsifies fats.

2. Converts albumin into albuminose.
3. Converts starch into glucose.

Amount of bile poured into the intestines daily; about 21⁄2 pounds.

Functions:

I. Assists in the emulsification of fats.

2. Stimulates the peristaltic movements.
3. Prevents putrefactive changes in the food.
4. Promotes the absorption of the fat.

Amount of blood in the body; from 16 to 18 pounds.

Size of red corpuscles; 32 of an inch.

Shape of red corpuscles; circular biconcave discs.

Shape of white corpuscles; globular.

Number of red corpuscles in a cubic millimeter of blood (the cubic of

an inch); 5,000,000.