Medical Officers of the Army of India.

59

      The walls of this cavity, however, are thickly beset with special secreting
villi or " nursing-filaments." Each of these nursing-filaments consists of a long
narrow arterial loop, a superficial capillary plexus which gives the filament a
scarlet hue, and a central vein—all held together by a minimum of connective
tissue. The meshes of the capillary network are filled by tubular follicles which
are either simple or slightly branched.

      These follicles, of which in Pteroplatœa micrura and Trygon bleekeri there
must be considerably over twenty thousand in each filament, secrete a glairy,
sticky, greasy fluid—sometimes creamy or pus-like in appearance—having
a heavy, sweetish, meaty smell, and containing many corpuscles and nuclei: it
coagulates when heated and leaves a greasy smear, which shows that it contains
albumin and fat, but no sugar has been detected in it.

      The spiracles of the fœtus are always widely open: in Pteroplatœa micrura
and sometimes in Trygon walga, bunches of nursing-filaments actually pass
through the spiracles into the pharynx of the fœtus; and in certain specimens
of Myliobatis nieuhofii and Trygon bleekeri their secretion has actually
been found unchanged in the spiral gut of the fœtus; so that there can be no
doubt that the secretion is swallowed and absorbed by the fœtus.

      The following papers refer to viviparous Elasmobranchs:—

         Everard Home, Phil. Trans. Roy, Soc. 1810, p. 208 (Acanthias). John Davy, Phil,
                    Trans. Roy. Soc., 1834, p. 531 (Torpedo).

         Johannes Müller, Müller's Archiv., 1837, p. lxvii (external gill-filaments, villi on
                    placental cord, etc.).

         Johannes Müller, Ueber den glatten Hai des Aristoteles, etc., in Abhand. Akad. Wiss.,
                    Berlin, 1840 (the classical work on this subject).

         Cantor, Ann. Mag. Nat. Hist., 1845, p. 372 (Zygæna).

         Leuckart, Zeits. Wiss. Zool., II, 1850, p. 254 (embryo of Torpedo).

         Hill, Ann. Mag. Nat. Hist. (2) VII, 1851, p. 353 (general).

         John Davy, Trans. Roy. Soc., Edinb., XXII, 1861, p. 491 (Rhina,Galeus,Acanthias
                    Centrina, Carcharias).

         Parker, Trans. New Zealand Inst. XV, 1882, p. 219 (Mustelus, Scymnus), and
                    XXII, 1889 (Mustelus).

         Haacke, Zoologische Anzeiger, 1885, p. 488 (uterus of Trygonorhina).

         Jungersen Zool. Anzeiger, 1885, p. 560 (remarks on Haacke's paper).

         Balbiani, Revue Scientifique (3) XXXVII, 1886, p. 732 (general).

         Haswell, Proc. Linn. Soc. N. S. Wales, 1888, p. 1716 (Urolophus, Trygon).

         Alcock, Journ. As. Soc. Bengal, 1890, pt. 2, p. 51 (Trygon, Myliobatis, Carcharias,
                    Zygæna).

         Mehrdorf, Zool. Jahresbericht fur 1891, Vertebrata, pp. 24 and 67 (general).

         Wood-Mason and Alcock. Proc. Roy. Soc., Vol. 49, 1891, p. 359, and Vol. 50, 1892,
                    p. 202 (Pteroplatæa, Trygon.)

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