GASTROSTOMY 



Gastrostomy (Gr. g aster, stom- 

 ach; stoma, mouth). Operation of 

 making a permanent artificial 

 opening into the stomach through 

 which food can be administered. 

 It is performed when there is a 

 stricture or obstruction of the 

 gullet, as, for instance, by malig- 

 nant disease, which prevents food 

 from being swallowed. Gastrotomy 

 is the operation of opening the 

 stomach. Gastrectomy is the 

 operation of removing the stomach. 

 See Stomach. x e 



Gastrula. Stage in the develop- 

 ment of a multi -cellular organism. 

 The single egg -cell develops by seg- 

 mentation into a hollow ball of 

 cells ; one side of the ball next 

 becomes indented, much as an 

 indiarubber ball may be dimpled, 

 and a thimble -shaped organism 

 results. This is called the gastrula, 

 and is very important as establish- 

 ing an inner and outer germinal 

 layer. In other words, it is the first 

 hint of an organism containing a 

 body cavity. See Embryology. 



Gas Works. Establishments 

 for the production of gas. Gas 

 works are now of two classes : first, 

 the familiar establishments where 

 domestic gas is manufactured, and, 

 secondly, works where gas is pro- 

 duced specially for use in metal- 

 lurgical operations and for the de- 

 velopment of power ; works of the 

 latter class are also styled gas- 

 power stations. 



Apart from the mechanical ap- 

 pliances for the handling of the 

 coal and other materials, the plant 

 of a gas works consists of the fol- 

 lowing elements. First the retorts, 

 long vessels of cylindrical or D- 

 shape cross-section, usually made 



3445 



of fireclay, in which the coal is 

 carbonised and the gas, with other 

 volatile products, driven out of it. 

 These were formerly fixed hori- 

 zontally in " benches " of six to 

 nine retorts ; more recently in- 

 clined retorts have been intro- 

 duced, while the most modern 

 plants have the retorts placed 

 vertically, the coal being intro- 

 duced at the top and the coke 

 removed from the bottom by me- 

 chanical appliances, the heavy 

 labour of charging the horizontal 

 form by hand being thus elimin- 

 ated. Secondly, the hydraulic 

 main, which is a large pipe running 

 across the tops of the benches of 

 retorts, and is normally partly 

 filled with tar and ammoniacal 

 liquor. A dip pipe connected by a 

 bridge pipe with an ascension pipe 

 from each retort has its outlet just 

 under the level of the liquor in the 

 main, so that the gas from the re. 

 tort will bubble through the liquor 

 into the upper part of the main. 



From the main the gas passes 

 through a " condenser," usually of 

 cast-iron pipes, where it is cooled, 

 and most of the tar and water 

 which it holds at this stage thrown 

 down. Scrubbers or washers to 

 extract ammonia and purifiers to 

 remove sulphur and other impuri- 

 ties succeed the condensers. 

 Finally, the gas is driven by a fan 

 or exhauster into the familiar 

 gas-holder or gasometer, passing 

 on its way through station meters 

 which record the volume. An 

 important section of many modern 

 gas works is represented by the 

 water gas plant, in which a mixture 

 of hydrogen and carbonic oxide is 

 produced bv passing steam through 



GATE 



incandescent coke ; this section 

 being generally supplemented by 

 an " oil gas " plant in which some 

 form of crude oil is more or less 

 gasified and mixed with the water 

 gas to form carburetted water gas, 

 the mixed product so produced 

 being used to supplement the heat- 

 ing and lighting power of other- 

 wise poor coal gas. 



Gas works also contain a con- 

 siderable number of other auxiliary 

 plant, particularly in connexion 

 with the recovery of by-products. 

 See Coal Gas ; Coal Tar. 



Gata, SIERRA DE. Mt. range of 

 Spain. Lying between the provs. 

 of Caceres and Salamanca, it is an 

 extension of the Guadarramas on 

 the E., their W. continuation in 

 Portugal being known as the Serra 

 da Estrella. The maximum eleva- 

 tion is 5,695 ft. 



Gate. Movable barrier in an 

 enclosing wall or fence to permit 

 ingress and egress. The principal 

 material for gates is wood or metal, 

 or their combinations. The utili- 

 tarian and military value of gates 

 was recognized as soon as man 

 began to raise fortified walls round 

 his towns or encampments ; they 

 were part of the defensive system 

 of every age. City gates were 

 largely employed by the Romans, 

 and during the empire they became 

 much more ornamental, though 

 they did not lose their military 

 character. The monumental gate- 

 ways of Rome had two passages, 

 one for entrance and another for 

 egress, and occasionally side pas- 

 sages for pedestrians only. These 

 were flanked by towers, square or 

 circular, and their summits were 

 nmchicolated. 



Gas Works. Diagram illustrating the arrangement of gas works, showing the course of the gas from the retorts through 

 condensers, scrubbers, and purifiers to the gasometer, and the collection of tar and ammonia by-products 



