PLACENTA (

See also:

• LAT

Lat. for a cake)  , in anatomy, the organ by which the embryo is nourished within the womb of its mother . When the young one is born the placenta and membranes come away as the " afterbirth." Inhuman anatomy the organ is a circular disk about seven or eight inches in diameter and one and a quarter inches in thickness at its centre, while at its margin it is very thin and is continuous with the foetal membranes . It weighs about a pound . In order to explain the formation of the placenta it is necessary to encroach to some extent on the domain of physiology . Before each menstrual period, during the child-bearing age of a woman, the mucous membrane of the uterus hypertrophies, and, at the period, is cast off and renewed, but if a fertilized ovum reaches the uterus the casting off is postponed until the birth of the child . From the fact that the thickened mucous membrane lining the interior of the uterus is cast off sooner or later, it is spoken of as the " decidua." The fertilized ovum, on reaching the uterus, sinks into and embeds itself in the already prepared decidua, and, as it enlarges, there is one part of the decidua lying between it and the uterine wall (" decidua serrotina " or " basalis "), one part stretched over the surface of the enlarging ovum (" decidua reflexa " or " capsularis ") and one part lining the rest of the uterus (" decidua vera ") (see fig I.) . Decidua basalis . under Alonzo de Ojeda, by whom he was entrusted with the charge of the unfortunate settlement at San Sebastian . He accompanied Balboa (whom he afterwards helped to bring to the block) in the discovery of the Pacific; and under Pedrarias d'Avila he received a repartimento, and became a cattle-farmer at Panama . Here in 1522 he entered into a partnership with a priest named Hernando de Luque, and a soldier named Diego de Almagro, for purposes of exploration and conquest towards the south . Pizarro, Almagro and Luque afterwards renewed their compact in a more solemn and explicit manner, agreeing to conquer and divide equally among themselves the opulent empire they hoped to reach . Explorations were then undertaken down the west coast of South America, in which Pizarro, though left. for months with but thirteen followers on a small island without ship or stores, persisted till he had coasted as far as about 9° S. and obtained distinct accounts of the Peruvian Empire .

The

governor of Panama showing little disposition to encourage the adventurers, Pizarro resolved to apply to the sovereign in person for help, and with this object sailed from Panama for Spain in the spring of 1528, reaching Seville in early summer . Charles V. was won over, and on the 26th of July 1529 was executed at Toledo the famous capitulation, by which Pizarro was upon certain conditions made governor and captain-general of the province of New Castile for the distance of 200 leagues along the newly discovered coast, and invested with all the authority and prerogatives of a viceroy, his associates being left in wholly secondary positions . One of the conditions of the grant was that within six months Pizarro should raise a sufficiently equipped force of two hundred and fifty men, of whom one hundred might be drawn from the colonies; as he could not make up his due complement he sailed clandestinely from San Lucar in January Glam.{ Dilated Part . 1530 . He was afterwards joined by his brother Unchanged part . Hernando with the remaining vessels, and when the expedition left Panama in January of the following year it numbered three ships, one hundred and eighty men, and twenty-seven horses . The subsequent movements of Pizarro belong to the history of Peru (q.v.) . After the final effort of the Incas to recover Cuzco in 1J36-37 had been defeated by Diego de Almagro, a dispute occurred between him and Pizarro respecting the limits of their jurisdiction . This led to battle; Almagro was defeated (1538) and executed; but his supporters conspired, and assassinated Pizarro on the 26th of June 1541 .