BLINDNESS 535 



and a half in length is made through the skin, 

 which is crossed by another at right angles to it. 

 The portion of bone above the cyst, and which in 

 general is felt to be more or less soft to pressure, 

 is removed by a circular saw termed a ** trephine," 

 or a hole is made by a "borer." The cyst is 

 punctured by a ''trochar," and the fluid withdrawn 

 by a ''syringe" applied to the ''canula." Care 

 must be exercised in the removal of the cyst. 

 When this has been effected, the parts of the skull 

 must be brought together, and crossed by slips of 

 adhesive plaster. Remove these in three days, and 

 wash the part with carbolic soap, if any matter 

 appears, and dress it in the same manner. Two 

 or three dressings generally is all that is required. 

 Mr Rhind, Surgeon, Edinburgh, describes, in 

 the first volume of the Edinbtirgh Journal of 

 Natural and Geographical Science^ a species of 

 worm, which was found in the frontal sinus of a 

 sheep ; but is unable to account for the animal 

 being found in such a cavity. It belongs to that 

 genus of worms called Pentastoma, and may be 

 specifically termed ovis. We have given a repre- 

 sentation of this worm on Plate xiv ; fig. 9, the 

 worm the size of nature ; fig. 1 1, the head magnified ; 

 fig. 10, the point of the tail ; fig. 8, a cross-section 

 of the body, showing the intestines. 



BLINDNESS. 



It may naturally be supposed that this malady 

 subjects the animal to the risk of accidents, and 

 consequently such as become blind should be fed 

 in an enclosure where there is no inequality of 

 ground. 



