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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    * sometimes backwards and oscillates from one side to the other, through the transverse vessels.® With most genera, the blood is red, being colorless with a few only, and it is always poor in corpuscles.® The Chaetopodcs have no lateral vessels. Their circulation is often due to pulsatory organs, and there is a great variety in the disposition of their vascular trunks and sinuses. With the Abranchiati, the dorsal vessel lies close upon the intestinal canal, and is almost wholly enveloped in the hepatic tissue. At the ante- rior extremity, it divides in many bifurcating branches, which, after encom- passing the pharynx, unite below it, and form the ventral vessel.® This vessel accompanies the ventral cord to the posterior extremity, and connects with the dorsal vessel by bifurcating branches, as before.(7) The transverse anastomoses connecting the dorsal and ventral vessel, form at each segment simple, or torose canals.® With the small Lumbricini, these are usually 4 The irregularity of the blood-currents has, un- doubtedly, given rise to the numerous different opinions upon the circulation of these animals ; see Dugis, Ann. d. Sc. Nat. XV. 1828, p. 30S ; Weber, in Meckel's Arch. 1828, p. 399 ; Muller, Ibid. p. 24 5 and in Burdach's Physiol. IV. 1832, p. 143 ; and Wagner, Isis, 1832, p. 635. If the valves which Leo (Muller's Arch. 1825, p. 421, Taf. XI. fig. 9) lias found in the dorsal and ventral vessels of Piscicola, should be found also with other Hiru- dinei, it would throw some light upon the real course of the circulation.* 5 With Sanguisuga, Haemopis, Pontobdella, Nephelis, Piscicola, and others, the blood is red •, it is colorless with some Clepsine, according to Fi- lippi (Lettera sopral’Anat. e losviluppo delle Clep- sine, 1839, Pavia, p. 11) ; it is also brown, violet or red, according to the species. He also declares (loc. cit. p. 8), that with Clepsine and Piscicola, which live wholly upon the blood of the lower animals, the * [§ 157, note 4.'1 The memoir of Gratiolet (Mem. sur. ^Organisation du systdme vasculaire de la Sangsue m^dicinale et de l’Aulostome vorace, pour servir d Phistoire des mouvements du sang dans les Hirudinees bdelliennes, in extract in the Comp. Rend. 1850, XXXI. p. 699), is worthy of a special reference in this connection. lie says : “ The lat- eral vessels, whose walls are very muscular, are the principal organs for the movement of the blood; they contract alternately, as has been well observed by Dugis, Weber Sind Muller, and their contained blood moves in a circular manner, sometimes one way, sometimes the opposite. “ The branches given off by these lateral vessels are of two kinds : “ A. Those destined for the skin, and which are ramified in the respiratory net-works ; they never anastomose with those of the opposite side. Before their final and minute ramifications, they form a large varicose net-work under the skin, which hith erto has been regarded as a plexus of hepatic ves- sels, but which is positively an interlacement of blood-vessels. “ B. The other branches are destined for the small intestine, and its spiral valve for the testicles, the copulatory apparatus, to the loops and to the muciparous vesicles. <;AU these branches arise from the branches or the large arches which form a free anastomosis between 15 vascular system communicates directly through small canals with the coeca of the digestive canal, so that the contents of this last may pass into the blood without being changed.! 6 See Hen/e, in Muller's Arch. 1837, p. 83, Taf. VI. fig. 5 (Enchytraeus), and Hojfmeister, De vermibus quibusdam, &c-, loc. cit. p. 14, Taf. II. fig. 4 (Saenuris variegata). 1 With Lumbricus, there are, beside the princi- pal ventral vessel, three others smaller, and in di- rect connection with the ventral cord. Two of these pass off laterally, and the third underneath ; see Leo, De Structura Lumbrici terrestris, p. 27; Dugis Ann. d. Sc. Nat. XV. 1828, p. 298; and Morren, loc. cit. p. 152, Tab. XXI.-XXIV. fig. 5, who especially has carefully described the vascular sys- tem of Lumbricus terrestris. 8 The transverse anastomoses are simple with Lumbricus, but torose with Saenuris ; see Hojf- meister , loc. cit. the two lateral vessels. The consequences of this form of structure may be easily summed up. The blood oscillates from the alternate contractions from one pulmonary net-work to another. It circu- lates in the principal organ of the intestinal ab- sorption, in the testicles, and in the muciparous glands. “ This circulation, very different from that which Dugis admits in the alleged pulmonary vesicles, shows how various are the means employed by na- ture. Here she determines the course of the blood by means of valves and stoppers ; while elsewhere she accomplishes the same end by causing certain blood-currents to prevail over others.” The valvular structure of the vessels with Pisci- cola, as mentioned by Z>o, has since been con- firmed by Ley dig (loc. cit.), who has found it also with Clepsine. Leydig calls the attention to another kind of circulatory system in Piscicola ; see loc. cit. p. 116. But this point has not yet been well made out; see also Mor/uin-Tandonr loc. cit. p. 133, PI. X. fig. 10, 15, 16, and PI. XII, fig. 13. -Ed. ! [ § 157, note 5.] The recent observations of Leydig (loc. cit. p. 119), have shown the blood of Piscicola to be always colorless. This view is proba- bly the correct one, since it better accords with the histological relations of the blood of these animals. — Ed.