HYDATIDS. 125 



Chapter XVII 



HYDATIDS IN MAN. 



The Anatomical Constitution of Hydatid Tumoues, and 

 THE Changes which they undergo. — The Chemical 

 Composition op these Tumoues. 



The hydatids in man, when in a perfect condition, 

 are rounded vesicles, formed of a substance similar 

 to coagulated albumen, which are free from any adhe- 

 sion to the tissue of the viscus which conceals them. 

 They enclose a limpid fluid, and generally contain 

 echinococci, which are either attached to the internal 

 surface of the vesicles, or float at hberty in the 

 hydatid hquid. 



The hydatids which are found in man are of a 

 very variable size ; sometimes they are scarcely per- 

 ceptible to the naked eye, and in other cases they 

 attain to the dimensions of the head of a foetus at 

 the full period of gestation. In the majority of 

 instances, their size ranges from that of a pea to that 

 of an orange. 



Their form, which is primitively spherical or oval, 

 is occasionally modified in a permanent manner by 

 the pressure of the surrounding parts wliich oppose 

 some obstacle to their regular development. 



Their walls are generally of an imiform thickness, 

 proportioned to the size of the vesicle, and they are 

 colourless and transparent, or of an opaque tint at 

 various parts of their extent. Accidental circum- 

 stances, such as the contact of a coloured fluid, of the 

 bile for example, give rise to change of colour. 



