ENTOZOA. 



131 



Digestive organs. We have already alluded 

 to the two leading modifications of the ali- 

 mentary canal, on which the binary division 

 of the Entozoa of Rudolphi is founded, viz. 

 into Sterelmintha or those in which the nu- 

 trient tubes, without anal outlet, are simply 

 excavated in the general parenchyma, and into 

 the Cttlelmintha, in which an intestinal canal, 

 with proper parietes, floats in a distinct ab- 

 dominal cavity, and has a separate outlet for 

 the excrements. In both these divisions the 

 mouth is variously modified, so as to afford 

 zoological characters for the subordinate 

 groups; and the alimentary canal itself in 

 the Sterelmintha presents several important 

 differences of structure. 



Cystica. The Cystic worms are generally 

 gifted, as in the species (Cytticcmu cellulose) 

 which occasionally infests the human subject, 

 w ith an uncinated proboscis for adhering to and 

 irritating, and four suctorious mouths for ab- 

 sorbing the fluid secreted by, the adventitious 

 cyst in which they are lodged. In the larger 

 Cysticerci lateral canals may be traced from the 

 suctorious pores extending down the body 

 towards the terminal cyst, but they appear 

 not to terminate in that cavity, the fluid of 

 which is more probably the result of secretion 

 or endosmosis. We cannot, however, partici- 

 pate in the opinion of Rudolphi,* that the 

 retracted head derives nutriment from the 

 surrounding fluid of the caudal vesicle, for if 

 that were the case, where would be the neces- 

 sity for an armed rostellum in addition to 

 the absorbent pores ? The frequency with 

 which the Cysticerci are found with the head 

 so retracted, may be attributed to the in- 

 stinctive action arising from the stimulus of 

 diminished temperature and other changes 

 in the surrounding parts occasioned by the 

 death of the animal in which the hydatid 

 has been developed. 



Ceatoidea. In the Cestoidea the digestive 

 apparatus commences for the most part by two 

 or four oral apertures, to which, in many spe- 

 cies (the Ta-nitf armatte), a central uncinated 

 proboscis is superadded, as in the Cysticerci. 

 Sometimes the mouths are in the form of oblong 

 pits or fossae, as in the Bothriocephalus latus, and 

 the allied species grouped under the same gene- 

 ric name ; or they have the structure of circular 

 suctorious discs, as in the Taenia solium and 

 other true Tania.-)- In both genera two alimen- 

 tary canals are continued back wards in a straight 

 line near the lateral margins of the body (e, e, 



* ' Osculis tamen canalibusque dictis omnem 

 aquae vim vesica caudal! collectam parari potuisse 

 vix credibile, sed hac parata vermem eandem 

 absorbere ideoqiie semper ferecaput huic immissum 

 offerre, longe aliam vero fluidi advehendi viam 

 dari, plurima suadent." Hist. Entoz. i. p. 279. 



t Many beautiful preparations, showing the 

 nutrient canals of the Tania solium injected with 

 coloured size and quicksilver, are preserved in the 

 Hunterian collection, (see Nos. 843, 844, 845.) 

 These were prepared, during the life-time of John 

 Hunter, and were presented to that great anato- 

 mist by Sir Anthony Cailisle, by whom they are 

 described in the ' Observations upon the Struc- 

 ture and (Economy of Taeniat,' in the second vo- 

 lume of the Linnaean Transactions, (1794). 



fig. 90), and are united by transverse canals 

 (f\ f t /g-90) passing across the posterior margins 

 of the segments. These connecting canals are 

 relatively wider in the Teenia solium than in the 

 Bothriocephalus latus, their size apparently 

 depending on the length of the segments, 

 which is much greater in the former than the 

 latter. Neither the transverse nor the longi- 

 tudinal vessels undergo any partial dilatations. 

 The chief point at issue respecting the digestive 

 organs of the Tape-worms is, whether the nu- 

 triment is imbibed by them through the pores 

 which occur at the sides or margins of each 

 joint, or whether the entire body is dependent 

 for its nutriment upon the anterior mouths from 

 which the lateral canals commence. The re- 

 sults of numerous examinations, which I have 

 made with this view, both on Bothriocephali* 

 and Taeniae, have uniformly corresponded with 

 those of Rudolphi, and I entirely subscribe to 

 the opinion of that experienced helminthologist, 

 that the marginal or lateral orifices of the seg- 

 ments are exclusively the outlets of the gene- 

 rative organs. 



In some species of Tape-worm, as the Tania 

 sphtenocephalus, in which no ovaria have been 

 detected, there has been a corresponding ab- 

 sence both of lateral and marginal pores, while 

 the lateral longitudinal canals have been pre- 

 sent and of the ordinary size. In the Tania 

 solium the generative pores being placed at 

 one or other of the lateral margins of the seg- 

 ments, the ducts of the ovary and testis (g, h, 

 fig. 90) cross the longitudinal canal of that 

 'side, and give rise to a deceptive appearance, 

 as if a short tube were continued from the 

 alimentary canal to the pore. But in the 

 Bothriocephalus latus and Bothriocephalus 

 Pythonis the generative pores open upon the 

 middle of one of the surfaces of each segment, 

 and in these it is plain that the lateral nu- 

 trient vessels have no communication with 

 the central pores. The orifices of the segments, 

 in short, correspond with the modifications of 

 the generative apparatus, while the nutrient 

 canals undergo no corresponding change. 

 Nutrition may be assisted by superficial ab- 

 sorption ; and, as Rudolphi suggests,! the se- 

 parated segments may for a short time imbibe 

 nutriment by the open orifices of the broken 

 canals ; but setting aside cutaneous absorption 

 and the more problematical action of the rup- 



* Principally on that species which infests the 

 intestines of the large serpent commonly exhibited 

 in this country the Python Tigris, Band. And we 

 invite the attention of comparative anatomists 

 interested in this point to an injected preparation 

 of one of these worms in the Museum of the Royal 

 College of Surgeons, No. 846 A. 



t " Al. Olfers (de veget. et anim. p. 35) 

 articulos Tteruae singulos ope absorptionis cutaneae 

 perparum, maxime autem ope osculi marginalis 

 nutriri contendit, sed osculum hoc vere ad genitalia 

 pertinfre in capite insequente evincam. Si cl. 

 vir absorptionem cutaneam minoris aestumat, hac 

 de re non litigabo, sed res alio modo explicari 

 potest. Annon enim ad vasa linearia nutnentia, 

 utrinque longitudinaliter decurrentia, si artituius 

 solufus est, in utroque ejus fine utrinque hiantia, 

 absorbendi officium deferri posset." Synops. Entoz. 

 p. 585. 



K 2 



