56 THE INTERNAL PARASITES OE 



coloured and life-sized figure, is copied from a careful 

 drawing made by the late Mrs. Cobbold, of Holywells, 

 Ipswich, Sept. 9, 1818. It supplies, nevertheless, a 

 tolerably characteristic representation of the echinococcus 

 disease as it shows itself in the lungs and liver of the 

 sheep. Occasionally the hydatids are very much more 

 numerous in the lung and liver than this figure 

 actually represents them to be. On the 22nd of May, 

 1873, I had an opportunity of exhibiting to my class a 

 remarkable example of the lungs and liver of a sheep, in 

 which there were several hundred cysts, so densely packed 

 together as to leave very little healthy lung and liver 

 tissue. Nevertheless the animal from which the diseased 

 organs were obtained was very fat, and had not dis- 

 played any symptoms of the disease. The animal was 

 sent from Norfolk, and was slaughtered for the London 

 market in the ordinary way ; no suspicions having arisen 

 as to the presence of internal parasites'. 



The literature of hydatid, or echinococcus disease, as it 

 manifests itself in the human bearer,is of enormous extent; 

 and this will not be wondered at when it is considered 

 that this parasite occasions not less than one-sixth of the 

 entire annual mortality in Iceland. In this country also 

 very many persons perish of the hydatid disorder, but it 

 comparatively rarely proves fatal to cattle. So incomplete, 

 however, are our records in respect of the prevalence or 

 otherwise of the common hydatid amongst oxen, that it is 

 difficult to draw any satisfactory inferences on this head. 



Experimental researches conducted by Yon Siebold, 

 Leuckart, Kiichenmeister, and others, have clearly estab- 

 lished the fact that all genuine forms and varieties of the 

 common hydatid are merely the larval stages of growth 

 of a minute tapeworm which resides in the dog (Taenia 



