<§.112. 



THE HELMINTHES. 



117 



CHAPTER VII, 



EESPIKATORY SYSTEM. 



§ 112. 



A respiratory system has not yet been found with, certainty in the 

 Helminthes. 



The pedunculated vesicles of many Nematodes, situated under the skin, 

 and projecting into the cavity of the body, and which have great absorp- 

 tive power, have been compared to trachean pouches and branchiae ; but 

 their structure is so little known, that any opinion as to their function 

 ought to be deferred. ''* 



A remarkable fact is the presence in some Trematodes of extremely 

 active vibratile lobules, situated intermittingly on the inner surface of the 

 walls of the vessels/-^ It may be questioned if these vessels have a special 

 function, difi'erent from that of the others. They somewhat resemble the 

 aquiferous system of the Polyps, Acalephs, and Echinoderms, and like it, 

 belong, perhaps, to the respiratory system. They differ, however, in not 

 having openings which communicate outwardly ; but, probably, they receive 

 by endosmosis, water absorbed by the skin.<^' But another objection to this 

 view, is, that in this order there has been found nothing like blood-vessels. 



belonging to the nutritive vessels. The nutritive 

 liquid of the vascular system differs from the 

 coarsely-granulated excretion of the excretory 

 organ, by its homogeneous and colorless aspect. 



It is remarkable that in Distomum tereticoUe 

 this liquid has a reddish color, which, in the finest 

 capillaries has a yellowish cast ; see fFiegmann's 

 Arch. 1835, I. p. 53. 



H. Meckel, liliewise, thinks that the above-de- 

 scribed vascular system of the Trematodes, is in 

 du'ect communication with the secreting organ 

 peculiar to these Helminthes ; see MuUer^s Arch. 

 1846, p. 2, Taf. I. fig. 2.* 



1 Bojanas (Isis, 1821, p. 187, Taf. III. fig. 51- 

 55) aflirms to have observed in Ascaris lambri- 

 coide.s these pedunculated vesicles, which are 

 found also in Ascaris depressa, and Strong-ylus 

 gigas, in connection with the lateral swellings ; 

 but this tlu-ows no Ught upon the nature of these 

 vesicles, for we are yet ignorant of that of these 

 swellings. The stigmata which he affirms (loc. cit. 

 p. 187, Taf. III. fig. 56) to have observed upon 

 these Unes with Ascaris acus, are, according to 

 my own observations, only subcutaneous cell-like 

 bodies. 



2 I have quite distinctly seen these vessels with 

 Diplozoon paradoxum, Aspidogaster conchi- 

 co/a, Distomu-m echinatum, and an allied species 

 of this last from the intestine of Falco apivorus. 



I am yet uncertain if the vibratile organs found 

 in the neck of Distomum globiporum and nodu- 

 losum {(Viegmanri's Arch. 1836, I. p. 218), and 

 in the parenchyma of Distomum duplicatum be- 

 hind the ventral sucker, are of the same nature. 



Ehrenberg {fViegrnann's Arch. 1835, II. p. 

 128) was the first who observed this ciliary move- 

 ment in the vessels of Diplozoon. When the 

 motions of these lobules are free, there is a rapid 

 current of the liquid, as Nordmann has remarked 

 (Microgr. Beitr. lift. I. p. 69). But if an animal 

 is cumpressed between two plates of glass, and 

 their rautions thus impeded, it will be quickly seen 

 that these last are the cause of the circulation ; in 

 fact, when the lobules cease moving, the colorless, 

 homogeneous, and, without doubt circulatory liquid, 

 is no longer perceived. 



3 Burmeister (Ilandbuch d. Naturgesch. 1837, 

 p. 523) compares, not without reason, this system 

 to the trachean system of insects, the first being 

 aqueous, and the second aerial respiratory organs, 

 thus confounding this vascular system of Helmin- 

 thes with the excretory organ and duct found in 

 most Trematodes. There may be, however, a com- 

 parison between these two systems, if we except 

 the insects with stigmata, and take those which are 

 aquatic and have a completely closed trachean 

 ajiparatus (see below), admitting no air from with- 

 out. 



* [ § 111, note 2.] Van Beneden (Ann. d. So. 

 Nat. 1852, XVIII. p. 23) has recently expressed 

 doubts upon the presence of a circulatory system 



with the Cestodes and Trematodes, but see the 

 beautiful plates of Blanchard, Ann. d. Sc. Nat. 

 1848, X. PI. XI. — Ed. 



