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
Catalogue details

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.

    141/482 (page 137)
    CHAPTERS VI. AND VII. CIRCULATORY AND RESPIRATORY SYSTEMS. §126. As yet, only a very imperfect vascular system has been observed in the parenchyma of these animals. With the Dendrocoeli, there are constantly two principal vessels, extending along each side of the body, which give off many lateral branches and anastomose together at their two extremi- ties. This system has no central heart-like organ, and the walls of the vessels not being contractile, the circulation is probably effected through the gen- eral contractions of the body.(1) The contained homogeneous and colorless liquid ought therefore to be considered as a nutritive fluid. With the Rhabdocoeli, the disposition is different. In many there are one or two vessels which traverse the body and loop at its extremities, without either giving off branches or diminishing in size. The movement of their colorless liquid is due to isolated vibratile lobules situated here and there in the vessels. This organization reminds one more of an aquiferous than a sanguineous system.® Special respiratory organs are here wholly absent, if we do not regard as such the aquiferous system just mentioned. There remains, therefore, only the conjecture that the ciliary epithelium upon the entire surface of the body is subservient to a general cutaneous respiration, by constantly bringing the water in contact with the skin. 1 Dugis has described and figured very com- pletely the vascular system of Planaria (loc. cit. XV. p 160, PL V. fig. 1, 2, XXI. p. 85, PI. H. fig. 24, 25). The cordiform organ which Mertens (loc. cit. p. 12, Taf. I. fig. 6, Taf. II. fig. 3) refers to the vascular system of Planocera sargassicola and pelfucida, is probably, as seen above, the central part of the nervous system. Dug Us is the only observer who affirms to have seen with the Den- drocogli proper movements of the vessels *, while Mertens, Ehrenberg (Abhandl. d. Berl. Akad. loc. cit. p. 243), Schulze (loc. cit. p. 18), and Ors- ted (loc. cit. p. 16), have observed only the con- trary. 2 With Derostomum leucops, Dug., I have seen two intertwined vessels of equal size through- out, extending from the caudal extremity to the head where they form a simple loop. At the cau- * [ § 126, note 2.] See for these two systems, Neue Beitr. zur Naturgesch. d. Wiirmer, &c., Schmidt, Die Rhabdoc, Strudelw. &c., p. 11, and p. 15. — Ed. 12* dal extremity, they approach so near to the cuta- neous surface that it is impossible to decide whether they terminate there by a loop, or open externally. Ehrenberg (Abhandl. d. Berl. Akad. loc. cit. p. 178, Taf. I. fig. 2) has figured two pairs of such vessels with Gyratrix hermaphroditus, and which loop at the posterior extremity, but in front termi- nate indistinctly. The trembling in the interior of these vessels observed by Ehrenberg, indicates certainly the presence of vibratile lobules, and which Orsted (loc. cit. p. 17, Taf. III. fig. 48) has distinctly found in the vessels of Mesostomum Ehrenbergii, while Foclce (loc. cit. p. 200) could see only their effects. These are the very vessels which this author supposes connect with the pha- rynx •, but this is not so according to my own ob- servations.*