MEDULLARY SARCOMA. 273 MEDUSA. all forms uf cancer, it runs the ipiickest course, soonest ulcerates, is the most malignant, and causes death in hy far the shortest time, often destroying life in a few weeks, or, at furthest, in a few months after its first appearance, unless it has been removed by an operation at an early stage. When it ulcerates, fungoid growths form upon the surface; they are extremely vascular, and bleed on the slightest provocation. In this state, the disease has received the name of fungus hamatoilcs. See Tumor. MEDUL'LA SPINA'LIS. See Nervous Sys- tem A.N 1 1 HraIN. MEDUM. ma-doom'. A village in Kgypt. on the western side of the Nile, some 40 miles south of Cairo, in about latitude 29° 30' N. Near it, on the edge of the desert. Ls the pyramid of King Snefru (q.v.), the first King of the Fourth Dy- nasty and the immediate jiredecessor of King Cheops (q.v.). From a great mass of rubbish, which covers its base, it rises in three stages to the height of about 122 feet, the upper stage being almost entirely destroyed. The outer walls consist of linely |)olished blocks of ilokattam stone, beautifully joined together. The pyramid was opened in 18.S1 by Maspero. who discovered a long passage leading from the north face into the se|)nlchral chamber, which is built upon the surface of the underlying rock. The chamber had. however, been rolibed as early as the time of the Twentieth Dynasty, and in it were found only some liroken fragments of the wooden culfin and a wooden jar. Flinders Petrie. who later made a careful examination of the pyramid, found against its eastern face a funerary chapel consisting of an open court and two small cham- bers. Ancient visitors to the chapel had left upon its walls numerous graffiti, in five of which Snefru is mentioned as the King to whom the pyramid was attribtited. Petrie's researches showed that the present peculiar form of the pyramid resulted from the removal of its outer layers in order to obtain stone for building pur- poses. Near the pyramid are the tombs (mastabas, q.v.) of a number of high personages of Snefru's Court. The most important of them are the mastabas. richly adorned with mural paintings, of Prince Rehotep and Nofret, his wife, and of Prince Nofer-ma't and his s]x)use. Yetct. The statues of Ke-hotep and Nofret, found in their tomb, are now in the ^luseum of Cairo. In the cemetery of Mediim have been found a number of graves exliibiting a peculiar mode of burial. The bodies lie upon the left side, with the face to- ward the east and the knees drawn up; coffins and the usual accessories of Kg^'ptian graves are absent. Consult Petrie, MerT.iim (London, 1892). MEDUSA. See GoRoo. MEDUSA (Lat., from Gk. iUdov<ra, Medousa, name of one of the three Gorgons, from fiideiv, nieitriii, to rule). . general name applied to the disk-like, lunbrella-shaped jelly-fish, with long marginal feelers, and so called from their re- semblance to the fabled Jledusa's head. (See Plate.) While the term medusa is now generally applied to the sexual free-swimming adult stage of any hydroid. it is particularly applicable to our conunon North Atlantic Aiirrlin fhividuhi of the class f>rtipho:oii (the group formerly called Discophora) . Another general name is acaleph. Our most aliunilant medu>a is Aurelia flavi- dula, which late in summer abounds along the coast from New York northward. It grows to the diameter of from eight to ten inches, becoming fully mature in August. Its rather tough jelly- FlO. 2. GA8TBULA OF AN AUKE- LIA-LIKE MEIJU.SA. a. Primitive month; h, gae- tro-vuscular cavity; c, ecto- derm; d, endoderm; e, meso- derm layer. Fig. 1. AURELIA FLAVIDULA. Adult, natural size, seen from above. like disk is moderately convex and evenly curved, while four thick oral lobes depend from between the four large genital pouches; the edge of the disk is minutely fringed to the ends of the ten- tacles. On the fringed margin are eight eyes, each covered by a lobule and situated on a peduncle, and occu- pying as iiuiny slight indentations, dividing the disk into eight slightly marked lobes. The subdivisions of the water-vascular ca- mils or tubes are very numerous and anasto- mose at the margin of the disk, one of them being in direct com- munication with each eye-peduncle, lien in motion the disk contracts and expands rhythmic- ally, on the average twelve or fifteen times a minute. On the approach of danger the animal sinks below the surface. Though it has lasso- cells, it is not poisonous to bathers, while the great Cyaitra arcticn is verv much so. The A u r e 1 i a spawns in late summer, the fe- males being distin- guishable by their yellow ovaries, the corres])onding male gland being rose- ate, w'hile the ten- tacles of the female are shorter and thicker than in the males. The eggs pass out of the mouth into the sea along the channeled arms, and in October the ciliated gastrula (Fig. 2) l)ecomes iiear-shaped and at- tached to rocks, dead shells, or seaweeds, and then assumes a hydra-shaped Scyphistoma stage (Fig. ,3), with often twenty-four very long tenta- Fkj. ;i. scvi'Hihtoma of Aurelia tiavklula, at different aoe8. Magiiifled. (.ilter AgasRiz. /
