HYDATID TUMOURS. 143 



by the discovery of the hooks of echinococci ; and 

 there would also be additional reasons for the sus- 

 picion that the tumour belonged to the hydatid class 

 if the matter which was expelled had the appearance 

 of pus, and presented under the microscope the 

 characteristics which have been already described as 

 belonging to the contents of atheromatous cysts. 



Hydatid tumours do not, of themselves, constitute 

 a grave affection, as they do not usually produce any 

 general derangement of the system, but they may be 

 attended by serious results on account of their situa- 

 tion or large size. 



The prognosis, being necessarily subordinate to 

 the diagnosis, cannot be established in the earliest 

 stages of the development of vesicular worms, nor 

 when these entozoa exist in some part which is 

 inaccessible to exploration. The cysts which are 

 situated in the limbs, in the parietes of the body, and 

 in other regions where surgical treatment can be 

 readily employed, may usually be cured without 

 much difficulty, and are not likely to prove fatal or 

 dangerous to life. Hydatid tiunours which, although 

 they have lasted for a long period, do not show any 

 further increase, or which even undergo an appre- 

 ciable diminution of size, may be regarded as already 

 tending to a favourable termination ; and the same 

 is also the case when a hydatid tumour has opened 

 either externally, or into some viscus which possesses 

 an external communication, and has not given rise to 

 any marked compHcations, whilst it has diminished 

 in size. 



Hydatid tumours are, on the contrary, very 

 serious when they occupy an important organ, when 



