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1 II. — Some observation a on the Natural History of the Eehinococcus 

 By Geokge Busk, Esq., F.M.S., &c. 



(Read November 13, 1844). 



By the Eehinococcus I intend to signify the minute animalcule 

 which is found in hydatid cysts in man and other animals. 



The simple cysts containing these animalcules, are always situated 

 in cavities in the interior of the animals infested by them. These ca- 

 vities may be situated in any part of the cellular tissue of the body, but 

 they are more usually found in the solid viscera, and most frequently 

 in the liver and lungs, especially in the lower animals. I farther as- 

 sume as proved, that all unadherent cysts, contained in such cavities 

 as these, are of the same kind, and that although they differ in some 

 respects in man and animals, they may be considered as of the same 

 species in both, and that they all, without exception, contain Echi- 

 nococci. And I farther express my conviction that these are the only 

 species of non-adherent cyst contained in cavities, at present known. 

 The proofs of these positions it would be perhaps out of place to ad- 

 duce on the present occasion, as such an inquiry would not come with- 

 in the scope of this Society. And I would only refer those who are de- 

 sirous of satisfying themselves on these points, to a very complete and 

 recent monograph on the subject of Echinococci, by M. Livois, to 

 which I am indebted for the greater part of the short historical notice 

 of the subject, which I will in a few words intrude on your attention 

 before proceeding to those points more immediately interesting to the 

 microscopic observer. 



The history of the Eehinococcus proves to us, that but little has 

 been added to our knowledge of it since the first description by 

 Pallas, in 1766, and who, had he been assisted by better optical ap- 

 pliances, would apparently have left little or nothing to be added, at 

 least up to a certain point. 



The animality of hydatids was first discovered by Hartmann, as far 

 back as the year 1685, and Tyson in 1691, and the subject was re- 

 sumed by Pallas in 1766 and the following years. 



He first recognized the probability that hydatid cysts were always 

 produced in connexion with an animalcule or worm similar to the 

 Cysticercus (Zeder), and he says "that it is probable that the non-ad- 

 herent hydatids sometimes observed in the human body, are either ;i 



