HYDATIDS IN THE BONES. 169 



nine in the extremities, of which only two were 

 situated in the upper, and the remaining seven in the 

 lower, limbs. 



It is doubtful whether some of these cases may 

 be looked upon as having been really due to hydatids, 

 or whether they were only cysticerci or serous cysts, 

 especially those cases which occurred in the eye, or 

 its appendages. 



The symptoms which are produced by hydatids in 

 the situations which have been mentioned, are similar 

 to those which are present when other tumours exist 

 in the same situations. 



Nineteen cases have been collected by Dr. Davaine, 

 of hydatids developed in the osseous system ; both 

 the long and flat bones have been known to be 

 affected. The following is a list of the various bones 

 in which hydatids have been observed, and of the 

 number of cases which have occurred in each bone : — 

 In the tibia six cases ; in the humerus, femur, frontal 

 bone, and pelvis, two cases each ; and one case each 

 in the temporal bone, sphenoid bone, and a phalanx 

 of the index finger. 



Generally speaking, the hydatids occupy the diploe 

 in the flat bones, and the spongy portion in the 

 long bones ; they have, however, been known to be 

 developed in the shafts of the long bones, and to 

 invade the whole extent of the medullary cavity. 

 Sometimes the hydatids occupy distinct cells in the 

 spongy tissue, but they are more frequently enclosed 

 in a single pouch. The development of this pouch is 

 very slow, and, in the majority of cases, its duration 

 has extended over several years. It may acquire the 

 dimensions of the closed hand. 



