Studies on the Physiology of Ascaris Lumbricoides

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ABSTRACT For the investigation of many aspects of the physiology of Ascaris lumbricoidis and other parasitic nematodes the provision of a fluid medium in which they can be kept alive and healthy in the laboratory is necessary. This is a matter of considerable difficulty, since the natural environment of such animals contains organic substances which are subject to bacterial action. Consequently, most of the experimental work which has been carried out has been on animals kept in saline solutions to which organic constituents were not added. In view of the fact that balanced salt solutions are usually employed in physiological work, it is somewhat surprising to find that solutions of sodium chloride have been used by many recent workers (see, for example, Hamisch, 1933, 1935; Hoffmann, 1934; Waechter, 1934; Kriiger, 1936, etc.). Dewitz (1899), however, used sea water in the case of an unidentified nematode from the tissues of Scomber scombrus. Some later workers, such as Slater (1925), Adam (1932) and Hirsch & Bretschneider (1937), used Ringer or Tyrode’s solution for Ascaris lumbricoides and Toryu (1934) kept Parascaris equorum in Ringer. Davey (1938), working with adult Ostertagia circumcincta and Fenwick (1939) with larvae of Ascaris lumbricoides, developed, by means of a series of survival experiments, saline media in which the animals could be kept alive in the laboratory for some days. Baldwin (1943) also used a balanced salt solution in which adult A. lumbricoides would survive for as long as 10-11 days, although the worms were undoubtedly unhealthy after the first few days in this medium. Hobson, Stephenson & Beadle (1951 ; and see Hobson, 1948), working with A. lumbricoides, in 1941 used 29% and, later, 30% sea water as a medium. In this, individual specimens have survived in apparently healthy condition for as long as 28 days. Baldwin & Moyle (1947) have used a medium based upon Eden’s analyses (see later in the present paper) of the body fluid of the same species. In this the animals did not five longer than in Bald-win’s original medium (Baldwin, 1943), although they remained more active. The composition of the various media to which reference has been made is given in Table 1.