PENTASTOMA TtENIOTDES. 399 



notion that we have to deal with an imperfectly- developed animal. 

 From one end of the body to the other there exists a central clear 

 space, and this is well defined by dark lateral masses, which narrow 

 out on either side of the head, in the form of a horseshoe- shaped 

 band enclosing the mouth and the four chitinous foot claws. These 

 dark patches, at first sight, look like vitelligene organs, but a 

 closer examination shows that they are entirely made up of large 

 parenchymatous cells, unconnected by any special fibres or tubes. 

 In an isolated and highly-magnified group of them, their granular 

 contents and central nuclei were at once rendered visible (as 

 shown in Plate XXI., Fig. 6), but some had become flattened at 

 the sides from pressure, and exhibited an angular outhne. 



In regard to the occurrence of this parasite in the human body, 

 I think it may be said that no one in this country has yet met 

 with it. My colleague. Dr. Murchison, during the time he held 

 the ofiice of Pathologist at the Middlesex Hospital, diligently 

 sought for it without success ; nevertheless, it appears that the 

 worm is not uncommon in the human subject in other parts of 

 Europe and elsewhere. The best record which has been pubhshed 

 on this head, is that given by Frerichs. In his excellent '* Clinical 

 Treatise on Diseases of the Liver," he writes as follows:* — " The 

 Pentastoma is a parasite which has only recently been discovered 

 in the human subject, but it is, nevertheless, far more common in 

 the human liver than the Echinococcus. It is devoid of chemical 

 importance, because it does not give rise to any functional derange- 

 ments. Pruner ('Krankheit des Orients,' 1847, s. 245) was the 

 first who pointed out the existence of the Pentastoma in the human 

 liver. On two occasions he found an encysted parasite in the liver 

 of negroes at Cairo, the nature of which, however, he did not 

 accurately determine. Bilharz and Yon Siebold (' Zeitschrift fur 

 "Wissensch. Zoologie,' Bd. iv., s. 63) recognized in it a new variety 

 of Pentastoma, to which they gave the name of P. constrictum. In 



* New Sydenham Society's Edition, London, 1861. Translated by Dr. Mnrchison. 

 Vol. ii., p. 276. 



