(-, -, -, -, ) , . , , . (, 1955; , 1959, 1963; , ., 1959; , , I960; , 1966; JRamachandran, 1946; Krautz, Zollfrank, 1957; Prior, Champion, 1962; Halperin, Na-hum, 1961; Nahum, Halperin, 1963; Matthews, 1958; Sen, Bishui, 1956; Logie, Urlau, 1957).

, , , , , . , , .

, . . , . 15.