ENTOZOA. 



117 



Acanthotheca ; and the singular organization 

 of the Syngamtu of Siebold, presently to be 

 described, clearly indicates the type of a third 

 order of Cavitary Entozoa. 



As a short description has already been 

 given of the species of Protelmintha which 

 inhabit the human body, we shall proceed to 

 notice those species belonging to the two di- 

 visions of Entozoa above defined, which have 

 a similar locality, before entering upon the 

 organization of the class generally. 



The first and simplest parasite which de- 

 mands our attention is the common globular 

 Hydatid, which is frequently developed in the 

 substance of the liver, kidney, or other abdo- 

 minal viscera, and occasionally exists in prodi- 

 gious numbers in dropsical cysts in the human 

 subject. 



Considerable diversity of opinion still exists 

 as to the nature of these ambiguous productions, 

 to which Laennec first gave the name of Ace- 

 phalocysts ; we shall nevertheless admit them 

 into the category of human parasites, for reasons 

 which are stated in the following descrip- 

 tion. 



The Acephalocyst is an organized being, 

 consisting of a globular bag, which is com- 

 posed of condensed albuminous matter, of a 

 laminated texture, and contains a limpid co- 

 lourless fluid, with a little albuminous and a 

 greater proportion of gelatinous substance. 



The properties by which we recognize the 

 Acephalocyst as an independent or individual 

 organized being are, first, growth, by intrinsic 

 power of imbibition ; and, secondly, reproduc- 

 tion of its species by gemmation." The young 

 Acephalocysts are developed between the layers 

 of the parent cyst, and thrown off either inter- 

 nally or externally according to the species. 



As the best observers agree in stating that 

 the Acephalocyst is impassive under the appli- 

 cation of stimuli of any kind, and manifests 

 no contractile power either partial or general, 

 save such as evidently results from elasticity, 

 in short, neither feels nor moves, it cannot, as 

 the animal kingdom is at present characterized, 

 be referred to that division of organic nature. 



It would then be a question how far its 

 chemical composition forbids us to rank the 

 Acephalocyst among vegetables. In this king- 

 dom it would obviously take place next those 

 simple and minute vesicles, which, in the 

 aggregate, constitute the green matter of 

 Priestly, (Protococcus viridis, Agardh;) or 

 those equally simple but differently coloured 

 Psychodiariee, wrn'ch give rise to the red 

 snow of the Arctic regions, (Protococcus Ker- 

 mesianus.) These " first-born of Flora" con- 

 sist in fact of a simple transparent cyst, and 

 propagate their kind by gemmules developed 

 from the external surface of the parent. 



Or shall we, from the accidental circum- 

 stance of the Acephalocyst being developed 

 in the interior of animal bodies, regard it, as 

 Rudolphi would persuade, in the same light 

 as an ulcer, or pustule, as a mere morbid pro- 

 duct? 



The reasons assigned by the learned Pro- 



Fig. 56. 



fessor* do induce us to consider the Acephalo- 

 cyst as a being far inferior in the scale of orga- 

 nization to the Cysticercus; but still not the less 

 as an independent organized species, sharing its 

 place of development and sphere of existence 

 in common with the rest of the Entozoa. 



Acephalocyst is endogena. Pill-box Hydatid 

 of Hunter, (Jig. 56). This species is so called 

 from the circum- 

 stance of the gem- 

 mules being detach- 

 ed from the internal 

 surface of the cyst, 

 where they grow, 

 and, in like man- 

 ner, propagate their 

 kind, so that the 

 successive genera- 

 tions produce the 

 appearance descri- 

 bed by Hunter and 

 other pathologists. 

 The membrane 



Acephalocystis endogena. 



of the cyst is thin, delicate, transparent, or 

 with a certain pearly semi-opacity; it tears 

 readily and equally in every direction, and 

 can, in large specimens, be separated into 

 laminae. The phenomenon of endosmose is 

 readily seen by placing the recent Acepha- 

 locyst in a coloured liquid, little streams of 

 which are gradually transmitted and mingle 

 with the fluid of the parasite. The vesicles or 

 gemmules, developed in the parietes of the 

 cyst, may be observed of different sizes, some 

 of microscopic dimensions, others of a line in 

 diameter before they are cast off, see fig. 56, 

 where a shows the laminated membrane, b the 

 minute Acephalocysts developed between its 

 layers. 



The Acephalocyst of the Ox and other Ru- 

 minant Animals differs from that of the Hu- 

 man Subject in excluding the gemmule from the 

 external surface, whence the species is termed 

 Acephalocystis exogena by Kuhl. Both kinds 

 are contained in an adventitious cyst, com- 

 posed of the condensed cellular substance of 

 the organ in which they are developed. 



The Genus Echinococcus is admitted by 

 Rudolphi into the Order Cystica, less on ac- 

 count of the external globular cyst, which, 

 like the Acephalocyst, is unprovided with a 

 head or mouth, than from the structure 

 of the minute bodies which it contains, 

 and which are described as possessing the 

 armed and suctorious head characteristic of 

 the Ccenuri and Cysticerci. It must be ob- 

 served that Rudolphi-f does not ascribe this 



* Mihi, quidem, ea tandem hydatis animal 

 vivum vocatur, quae vitam propriam degit uti Cys- 

 ticerci, Coenuri, &c. Quae autem organismi alieni 

 (v. c. humani) particulum efficit animal, me 

 judice, dici nequit. Mortua non est, quamdiu 

 organismi partem sistit, uti etiam ulcus, pustula, 

 effiorescentia ; sed haec ideo non sunt animalia. 

 Synops. Entoz. p. 551. 



t Vermiculi globosi, subglobosi, obovati, obcor- 

 dati, etc.; pro capite plus minus vel exserto vel 

 retracto ; postice mox obtusissimi, mox obtusi, mox 

 acuti. Corona uncinulorum, uti videtur, duplex. 



