again. A simple case of circulation is illustrated in the crayfish, where the heart consists of a single chamber with muscular walls. When it contracts, the blood is sent, in arteries, forward, backward and downward; on its return path it passes through the gills. In the clam there is a two-chambered heart. In fishes there are two chambers; in frogs and toads three; in the highest reptiles and all birds and mammals four chambers in the heart. The ancients believed that the arteries contained air, and only the veins blood. Galen (131-200), in the 2d century, demonstrated that both arteries and veins contain blood, but a direct connection between the two was not thought of. In the 16th century such a connection was believed in by Vesalius and others. In 1628 William Harvey published a book in which he maintained that the quantity of blood leaving the heart and the rate at which it leaves made a return to the heart necessary. This marks an epoch in physiology. He did not, however, see the minute vessels connecting arteries and veins. It remained for Malpighi, in 1661, and Leeuwenhoek, in 1669, to demonstrate, with the microscope, the existence of minute tubes connecting arteries and veins, and thus to show that the circulation takes place in a series of closed tubes. For further facts regarding circulation see Heart.
Cir′cus, in Roman usage, was a large, oblong building, used for chariot and horse-races, athletic exercises and wild-beast fights. According to tradition, circuses originated with Romulus, and subsequently these games became popular, and several buildings were put up for their use, the largest being called the Circus Maximus. This was enlarged several times, and is reported to have held from 150,000 to 385,000 persons. In the time of Julius Cæsar it was 1,875 feet in length and 625 feet wide. It was oblong in form, rounded at one end and square at the other, with tiers of stone seats on the sides and curved end, while at the square end were stalls for the horses and chariots. The Romans were very fond of the chariot-race. Usually, four chariots raced seven times round the circuit. Boxing, wrestling and even battles were engaged in. Canals were also dug and sea-fights shown. Animals were brought from as far as Asia and Africa. Free shows were given by politicians to curry favor with the people. Pompey gave a five days' circus, during which 500 lions and 20 elephants were killed. Often the Romans would demand bread and circus-games from candidates for office.
Citizenship. The term citizen implies membership in a political community, and involves on the one side his allegiance to and support of that community, and on the other the protection of the citizen by the community. It does not imply the right to vote or to hold office. These privileges may be and often are withheld from citizens, while granted to those who are not citizens. This modern use of the term citizen must be contrasted with the original use, which prevailed among the Greeks, and which is thus defined by Aristotle: A citizen is one who has the right to take part in both the deliberative and judicial proceedings of the community of which he is a member. Our idea of citizen is related to that of subject, as that term was used in England when this country separated itself from England; for a subject meant one who owes allegiance to the king and demands protection from him. The country with us takes the place of the king,—that is the difference. By the original constitution of the United States it was left uncertain whether citizenship related in the first place to the state and only secondarily to the nation, or vice versa. The fourteenth amendment, passed by Congress in 1866, approved by the requisite number of states and proclaimed law in 1868, decrees that all persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. This made national citizenship fundamental, and declared that state citizenship follows from it. Those living in territories and the District of Columbia are not citizens of any state, though they may be citizens of the United States.
Citizenship does not rest on descent, fundamentally, but on the fact of birth on the soil of the United States. A person born of alien parents on the soil of the United States, unless he reserves allegiance to the country of his parents, is a citizen. Exceptions are Indians not taxed and persons born in the Philippine Islands until they shall be declared a territory (Supreme Court decision, May 1901). Citizenship is extended to those born abroad of a father who is a citizen, and to an alien woman married to a citizen (Acts of Congress, April, 1802, and Feb., 1855). The third extension of citizenship is to naturalized persons. To be naturalized the alien must have declared his intention to become a bona fide citizen at least two years before admission, must have resided in this country five years, and must swear that he does not believe in polygamy or disbelieve in organized government. He must speak English. An alien landing before he is 18 may be naturalized at 23 without a previous declaration of intention. The fourth extension is to one whose father is an alien, and who himself was born abroad, but who is under 21 and resides in this country when his father is naturalized.
