Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett.

  • Karl Theodor Ernst von Siebold
Date:
1854
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Licence: Public Domain Mark

Credit: Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    of the intestinal canal; these are narrow and their botryoidal extremities lie in the interstices of the dorsal wall of the body. With Aphrodite aculeata, the structure is analogous but differs in that these appendages have more the aspect of coeca with thin walls, and have not the ramified diverticula except in their central part and between the already-mentioned saccular dilatations.(7) As an hepatic organ may be regarded with more certainty a particular tissue colored in part brownish yellow, and partly greenish yellow, which closely surrounds the whole intestinal canal of most Annelides. Carefully examined, this tissue is found composed of closely-aggregated glandular sacs which empty their contents into the intestine either directly, or by many common excretory ducts.<a> This contained liquid is, with most species a transparent fluid in which are suspended brown granules, and it resembles the bile of the higher animals. C II APT Ell VI. CIRCULATORY SYSTEM. § 156. This system is highly developed with the Annelides. The blood is usu- ally colored, and the vascular system, remarkable for many peculiarities, is complete and closed. This system may be divided into a central and a peripheric part. The first consists of large contractile vessels taking the place of a Heart. There are also various heart-like organs in the shape of varicose dilatations upon the course of the contractile vessels. The principal ves- sels have a longitudinal course, occupying the whole length of the median line of the body, — one as a dorsal, and the other as a ventral vessel. With many Hirudinei, there are also lateral vessels. The dorsal and ventral vessels unite at both extremities, beside anastomosing by transverse branches in the separate segments. When there are lateral vessels, these also connect with the median ves- 7 See Pallas, Trcviranus, Milne Edwards, loc. cit., and Grube, loc. cit. p. 54. & According to Henle (Muller's Arch. 1837, p. 81, Taf. VI. fig. 2), this glandular envelope forms a villous envelope about the intestine. This is also true of Lumbricus, Lumbriculus, Nais, and Chaetogaster. The glandular sacs are greenish with Branchiobdella (Henle, loc. cit. 1835, p. 575), yellowish with Amphitrite (Rathki, Danzig. Schrift. loc. cit. p. 65). With Sanguisuga, the ex- cretory ducts of the hepatic sacs inter-anastomose and form a kind of net-work around the stomach and its coeca 5 see Brandt, Med. Zool. p. 247, Taf. * { § 155, note 8.] The hepatic organs with the Annelides have been successfully studied by Will (Muller's Arch. 1848, p. 508), who has used chem- ical tests. lie has found the glandular layer XXIX. A. fig. 28, 29. With many, this hepatic layer envelops also the blood-vessel upon the dorsal surface of the intestine. It is passible that the yellow canal described by Morren, with Lumbri- cus terrestris as Chloragogena, is only this hepat- ic mass (loc. cit. p. 142, Tab. XV. XVI.). Another canal which is traversed by blood-vessels and closed at both extremities, and which is contained in a longitudinal enlargement upon the internal sur- face of the intestinal canal, and is called by Mor- ren , Typhlosolis (loc. cit. p. 13S, Tab. XI. XII. XVI. XVII.) may perhaps be regarded as a recep- tacle of chyle.* (Lumbricus, Nais), and the long, thread-like and coecal glands (Hirudo, Haemopis, Aulacostoma, Jfelluo, Piscicola, Clepsine) which surround the intestinal canal, to be organs of this nature. — Ed.