Page:The New International Encyclopædia 1st ed. v. 17.djvu/827

* SECRET ASSOCIATIONS. of which have existed from very aneieiit times. (For the rule played by the Bo.wrs in the up- rising of HIOO. see CilTNKSK K.mi'ire.) Many so- cieties are ostensihly pliilaiitlinipic, and some are imrely benevolent, providing for marriage, burial, and business loans. In the Vnited Stales there are many secret societies, in which, however, the fraternal element largely predominates. See So- cieties. Consult: IIec!<thorne, Secret Sociclirs of All Afics (London. IS!)!)), which contains a bil)liog- rapliy. SECRETION ( Lat. srcrcliu, separation, from sccrctns, secret, separate). A physiological proc- ess by which certain materials are separated from the blood to form new substances called secre- tions, through the agency of certain liighly spe- cialized cells. These materials are of two kinds: true secretions, which have some definite function to perform in the animal economy, and excre- tions, which are discharged from the body as use- less or injurious. Secretions are further distin- guished by the fact that they do not exist :ilready formed in the blood, but require for their produc- tion special cells and a process of elaboration ; while excretions are merely abstracted from the blood in the same form in which they already oc- cur in that Huid. Both secretion and excre- tion contribute to health and nutrition, the one by performing some positive function, as aiding di- gestion, the other negatively by freeing the body of the products of destructive metabolism, which if retained would cause disease. Secretion is performed by the following or- gans : The serous and synovial membranes ; the mucous membranes, with their special glands, buccal, gastric, and intestinal; the salivary glands and pancreas; the mammary glands; the liver; the lachrymal glands; the kidneys and skin ; and the testes. Secretion takes place by two different processes, the one physical and the other chemical. The physical processes are those of filtration and dialysis; the chemical process is one of true secretion. Both processes are em- ployed in the secretion of the urine; the former within the Malpighian bodies and the latter in the tubuli uriniferi. (See Kidneys.) The simplest form of secretion is that of the serous and synovial membranes, the pleura', the pericar- dium, peritoneinu, and the lining of the joints. These are lubricated by a fluid transuded di- rectly through the flat endothelial cells lining these mendiranes from the blood vessels beneath them. A somewhat more elaborate process is that of the mucous membranes lining the respiratory and gastro-intestinal tracts. Thousands of cy- lindrical recesses, known as tubules, paved with secreting cells, empty their peculiar secretions upon every square inch of these Surfaces. An isolated group of such tubules emptying by a single duct is called a simple gland: several of such grou])s having a common single duct con- stitute a compound gland ; and the larger glands are simply nuiltiplications of these groups, and serve to increase the amount of secreting surface within a given space. For a description of the manner in which cells are arranged in the vari- ous glandular structures, .see Glands; Kidney; Liver : MicoUiS Mejibr.?;es ; etc. The charac- ters of the various secretions, among which may be mentioned saliva, gastric juice, pancreatic juice, bile, ordinary mucus, sweat, tears, urine, r49 SECRET SERVICE. the products of the serous and synovial mem- branes and the sebaceous glands, are described under their own names or tlio.se of the organs which produce tlicni. SECRETION, The process in plants by «liicli a substance is formed and expelled from a C(dl, or the substance which is so formed. The term is usually restricted to the fornuition of the many and diverse special materiaK, such as enzymes, resins, volatile oils, and sugars, wliieli are of service lo the plant. Secretions are either ]ioured out upon the surface or into internal rc- ceplaeles. See Gland. The formation of the secretion may be either direct or through the production of lin interme- diate substance. The details of the elaboration, however, are still obscure. For example, sugar is supps<'d to be formed directly, whereas enzymes are usually preceded by (be" proiluctioil of minute granules of zymogen in the proto- plasm. This distinction may mean only that in some cases visible products precede the final one, while in others they do not. There are two modes of separation of the secretion from the profoplasm. In the first the cell wall remains in- tact and the secretion is either expelled through the jiermeable parts of the wall, anil appears first in its ])roper nature beneath the inipernu-alile cuticle, which it lifts into a blister, or through these permeable parts into an intercellular recep- tacle. No satisfactory explanation of the process has been found. Such glands may secrete once only, or repeatedly, or continuously. In the second method the secretion results from the disorgan- ization of the protoplasm which it eventually re- places. In multicellular glands the cell walls disappear and after one secretion the glands perish. If the secretion be soluble in water, e.g. sugar, as in many nectaries, and by exposure to the air the solution becomes concentrated, its osmotic pressure (see Osmosis) may be so in- creased that it withdraws water from the cell. Nectar is thus kept fluid and ready for the in- sects which it attracts. SECRET SERVICE. The name given to that departuunt of a govcrniiK'nt whose business it is to detect crime and fraud, obtain information of various kinds, and render various services of a secret nature. Its duties are generally not de- fine<l, and vary with the necessities of the occa- sion which may create (hem. In the I'nited States the service is not centralized as it is under most foreign governments, and each executive de- partment employs men to detect specific classes of offenders against the laws. The name has come to be generally applied to the Secret Service Pivision of the Treasury Department, organized in 1S64 and charged chiefly with the detection and arrest of counterfeiicrs, the whole country being divided into 27 secret service districts. Op- eratives from the division, however, are fre- quently detailed to work in connection with other (iepartnients than the Treasury Department. Thus during the Spanish-.Xmcriean War secret service oiieratives rendered efTective services in breaking up the Spanish secret service organiza- tion in the United States. The Treasury De- partment also employs men to detect infractions of revenue laws and bring ofTenders to justice. The War Department employs men to obtain in- f(uniation of various kinds, and within the Post Ofliee Department there is an efficient division of