SLEEPER. A term used with many technical applications for a piece of timber, metal, etc., used as a support; in carpentry it is such a piece of timber laid on low cross walls as a plate to receive ground joists; in shipbuilding, a strengthening timber for the bows and stern frame. The most frequent use of the term is for a timber or steel support on which the chairs are fixed for carrying the rails on a railway; in America these are more com monly called "ties" (see RAILWAYS). It is an error to derive the word from "sleep." Its real source is the Norwegian sleip, mean ing a roller or timber laid along a road. This word Skeat (Etymol.
Dict., 1898) connects with "slab." The French term dormant which is equivalent to "sleeper," is used for a part of the frame of a window or door which cannot be opened.
Sleeper is also used as an abbreviation for sleeping car.
(Trypanosomiasis), a parasitic disease, familiar among West African natives since the beginning of the 19th century, and characterized by protracted lethargy, fever and wasting. It is caused by the Trypanosoma gambiense, a parasite which was discovered in the frog by Gruby in 1847, and in 1880 by Griffith Evans in horses afflicted with the dis ease called "surra" in India. In 1895 Surgeon-Major (after wards Sir) D. Bruce found a trypanosoma similar to Evans's in cases of what was known in cattle as "tsetse-fly disease"; and though the trypanosoma had not then actually been found in man, Bruce suggested that this was akin to the human "sleeping sickness" which had now extended into the Congo Free State, Uganda and elsewhere, and was causing great mortality, many Europeans having died of the disease. In 1903 Castellani found the trypanosoma in the cerebrospinal fluid of human patients afflicted with the disease. The pathology of "sleeping-sickness" was vigorously taken up, and in June 1907 an international con ference was held in London to organise research.
The problems were : (I) to determine whether the tsetse fly (glossina palpalis) was a direct or indirect conveyor of the para site; (2) whether the parasite underwent necessary develop mental changes in the tsetse fly; (3) if so, whether the developed germs were conveyed by the original fly or its larva when ar rived at the imago stage; (4) how long an infected glossina pal palis remained infected; (5) whether other species of glossina were concerned; (6) the geographical distribution and habits of the fly; (7) whether and how far the spread of infection was the work of any of the vertebrate fauna (other than man) ; (8) to suggest preventive methods for exterminating the glossina, or protecting uninfected districts by segregation or otherwise; (9) to study the therapeutics of the disease.
During the process, which occupies 14-28 days or more, the fly is not infective, but when the germs are established in the salivary glands it regains its infectivity and may retain it for a long period, for at each feed germs are poured into the punc ture. Unless the salivary glands contain the germs a fly is not capable of infecting, but only in a small proportion is this de velopment completed ; in nature the proportion cf infected flies rarely exceeds one in 1,000. Conveyance is therefore indirect. Direct infection may occur in nature, but the failure of the dis ease to spread in the absence of tsetse, even though biting in sects of many kinds are present, seems to show it must be rare, e.g., hundreds of cases of sleeping-sickness were recorded in the West Indies among slaves brought from Africa, but there is no recorded instance of spread in the New World. The disease was formerly rife in the island of Principe in the Gulf of Guinea, where G. palpalis abounded, but no cases occurred in the neigh bouring island of San Thome, with the same insect fauna, but, like America, with no tsetse. Duke believes that when the dis ease is epidemic direct infection is the rule. There is no evidence that the fly can transmit the germs to its offspring. The fly has been shown to be capable of infecting for at least 96 days.