128 



ENTOZOA. 



in retracting the head within the terminal cyst ; 

 and this part, in the same specimen also, pre- 

 sented a remarkably distinct series of transverse 

 striae, indicating most probably the circular 

 fibres which contract the cyst in the transverse 

 direction, and protrude the proboscis.* This 

 species of Hydatid, which is common in the 

 abdomen of Sheep, where it is either sus- 

 pended in a cyst to the mesentery or omen- 

 turn, or embedded in the liver, &c. has been 

 the subject of numerous observations, and is 

 generally selected to demonstrate the muscular 

 phenomena in an animal of very simple orga- 

 nization. When extracted from a recently 

 killed sheep, and placed in water at the blood- 

 heat, the cyst may then be observed to become 

 elongated, and agitated with undulatory move- 

 ments ; the retracted part of the body is thrust 

 forth, and again, perhaps, drawn in ; during 

 the latter action the anterior part of the cyst 

 becomes wrinkled and is drawn back, gliding 

 into the posterior part of the cyst; the anterior 

 part of the body is at the same time retracted, 

 and is received into the posterior ; and thus by 

 degrees the head and all the body become 

 concealed in the terminal cyst. 



In the Cestoidea the muscular structure is 

 indicated slightly by impressions on the sur- 

 face of the body, but it is seldom that a distinct 

 layer of muscular fibres can be demonstrated. 



To the worms of the genus Caryophylleus 

 both Zeder and Rudolphi agree in ascribing 

 longitudinal fibres, which extend along the 

 anterior part of the body and transverse 

 fibres, which are conspicuous in the pos- 

 terior segments. In the T&nia both trans- 

 verse and longitudinal strata of fibrils are stated 

 to exist,f obscure indeed, or almost impercep- 

 tible in the smaller species ; but more evident 

 in the larger specimens, in which, according to 

 Rudolphi, each segment has in general its own 

 strata, whence it enjoys, for some time after 

 being separated from the rest of the body, 

 distinct and peculiar motions; and such joints 

 have been described as distinct species of En- 

 tozoa, under the name of Cucur- 

 Fig. 75. bit'ina. In the Bothriocephalus 

 latus, on the other hand, the lon- 

 gitudinal fibres are continued from 

 one joint to another, whence the 

 segments are less readily separable, 

 and a common and continuous co- 

 vering may be dissected from off 

 the body of this species. 



Living Taeniae placed in warm 

 water exhibit undulatory motions. 

 The body of one of these worms is 

 sometimes found to be tied at some 

 part in a complicated knot, as seen 

 in jig. 75, doubtless by means of 

 these motions. The Ttenia solium, 

 when recently expelled from the 

 body by the irritation of a vermifuge 

 solium. remedy, is occasionally contracted 

 to the length of a few inches, the 



* See Preparation, No. 409 A, Physiological 

 Series Mus. Roy. Coll. of Surg. Catalogue, vol. i. 

 p. 115. 



t Rudolphi, Hist. Entoz. i. p. 223. 



segments appearing as close-set transverse striae ; 

 when placed in water, after a few hours it will 

 have returned to a length of as many feet. 

 Werner* relates an instance of a Taenia which 

 extended from the anus of a patient to the 

 length of three feet, and which returned itself 

 almost wholly into the intestine, the dependent 

 part being drawn upwards by the superior. 

 Other and still more extraordinary instances of 

 the movements of the Cestoid worms are on re- 

 cord ; but that the separated joints of the Ttenia 

 solium should be able to creep several feet up a 

 perpendicular wall could scarcely gain a mo- 

 ment's credit, if the fact were not related by 

 no less distinguished a naturalist than Pallas.f 

 In general the muscular fibres cannot be 

 observed in the diaphanous bodies of the 

 smaller Trematoda, yet every part is endowed 

 with active contractility : in the larger species, 

 however, both longitudinal and transverse strata 

 of fibres may be demonstrated in the tegumen- 

 tary muscular covering of the body ; both which 

 we have distinctly seen in the large Distoma 

 clavatum. The muscular fibres of the aceta- 

 bula are disposed in two series, one radiating 

 from the centre to the circumference, the other 

 in concentric circles. The muscular tissue is 

 also well developed around the base of the 

 sucker, by which the animal is enabled to pro- 

 trude them from the surface. 



In the Planaria, in which, as in the T<zni<e, 

 according to our observations, the muscular 

 system is indicated only by striae on the super- 

 ficies of the apparently homogeneous paren- 

 chyma, the phenomena of muscularity are 

 strikingly displayed in the varied and energetic 

 actions of the living animal. They lengthen, 

 shorten, widen, contract, or contort the body in 

 various degrees and directions : their mode of 

 locomotion on a solid plane is by an insen- 

 sible undulation, or successive approximation 

 of small proportions of the body, producing 

 a gliding movement, as in the Slug; and the 

 same actions take place in swimming through 

 the water, except that the body is reversed ; 

 and the ventral surface turned upwards, as in 

 the Carinaria and other aquatic Gastropods. 

 When seizing a living prey, as in Jig. 76, the 

 contractions of the body 

 Fig. 76. are more vigorous and 



extensive. 



In the Echinorhynchus 

 the muscular fibres are 

 of a whitish colour, semi- 

 transparent, and of a ge- 

 latinous appearance; they 

 Planaria lactea (B), are eminently contractile, 

 feeding on a Nais. and readily respond to 

 the application of both 

 chemical and physical stimuli. Cloquet ob- 

 served them to contract under the influence of 

 the galvanic current six hours after the cessation 



* As quoted by Rudolphi. ' Taenia ad trium 

 ulnarum longitudinem ex mulieris ano propen- 

 dens, in casu qnem Wernerus (1. c. 47) refert, 

 tola fere in pristinum hospitium rediit, pars pro- 

 pendens itaque a superiore sursum ducta : similes 

 oinnino casus Andryus habet.' Ibid. p. 223. 



t Also quoted by Rudolphi, p. 223. 



