316 Miscellaneom. 



After commenting upon the vague manner in which the term hydatid 

 has been appHed in practical medicine to every abnormal production 

 having the form of a cyst, the author proposes to limit it to the fol- 

 lowing definition : — " Every vesicular production found in living or- 

 ganized tissues which is provided with spontaneously moving organs, 

 or which has at least the power of reproduction apart from the tissue 

 in which it is lodged by giving birth to individuals similar to itself." 

 He then gives a sketch of the specific characters of the different spe- 

 cies included under the names oi Hydatis spuria, Acephalocystis, Ecki- 

 nococcus, Polycephalus or Ccenurus, and Cysticercus. The first of these, 

 commonly met with in the brain and spinal marrow, and which con- 

 sists of one or more simple cells filled with fluid and containing some 

 minute globules, has, he says, been almost always confounded with 

 the true hydatid or Acephalocyst, whereas it is not a distinct animal, 

 but consists of certain elementary cells of the tissue, which by a pro- 

 cess of normal (abnormal ?) evolution have become isolated from the 

 rest of the organism, and are capable of maintaining an independent 

 existence. This opinion will be seen to coincide very closely with 

 that of Prof. Owen in his Hunterian Lectures relative to the Ace- 

 phalocyst, namely, " that it is a gigantic organic cell, not a species of 

 animal, even of the simplest kind ;" but the cellules of this species he 

 regards on the contrary as true organized beings, having the power 

 of generation, and in the latter part of the paper adduces reasons for 

 regarding them as but a primary form of the Echinococcus ; 1st, from 

 his having found the latter chiefly in different aquatic animals, such 

 as tortoises, frogs, fishes and water-birds, also in mammalia and man ; 

 2nd, from having found in clear spring- water some small pyriform or 

 lanceolated animalcules -^q^ of a Paris line in diameter, which had 

 instead of a coronet of hooks a disc covered with radiating striae, and 

 furnished in its centre with only a single spine ; 3rd, that these ani- 

 malcules were so exactly similar in form and character to the Ace- 

 phalocysts at the period of their transformation into Echinococci, that 

 no appreciable difference could be detected either by himself or other 

 skilful observers between them. He thinks it not improbable there- 

 fore that the Echinococci may exist in nature, if not in a perfect 

 form, at least as ovules, in the water, and that with it they are in- 

 troduced into the bodies of different animals, there to undergo further 

 development, and that they may then work their way by means of 

 their hooks from the intestinal canal into the interior of the tissues, 

 and from their very minute size, even into that of the circulating 

 system. It is curious to compare our author's statement upon the 

 identity of the Acephalocyst and Echinococcus, with one recently 

 made by M. Eugene Livois in a work called * Recherches sur les 

 Echinocoques chez I'homme et chez les animaux,' Paris, 1843, who 

 asserts " that no good examination has been yet made of the cellules 

 of the Acephalocyst ; that they are in reality clusters of Echinococci 

 whose head is not yet protruded, but which, when they have at- 

 tained their full development, separate, and are found floating in the 

 fluid of the sac, and that in upwards of 800 examinations he never 

 found these parasites absent in a single hydatid." Leaving this 

 question as one still open to further investigation among microsco- 



