296 ARACHNOIDEA, 



c/^E varies in length, being sometimes as much as five of six lines in 

 extent, and at its termination, under a slight elevation of the skin, 

 the little inhabitant lies concealed. The mite may be easily dis- 

 tinguished by the experienced eye, as a small dark point at the 

 end of the burrow, and if a thin capsule of skin be raised in this 

 situation with the point of a needle, the little creature is brought 

 into view. 



The spot or streak, which is here described, is not met with on 

 all the vesicles, for the same animal may excite a series of these 

 in its course ; and a number may be developed in the vicinity of 

 its habitation, while it is in the primitive vesicle alone — that 

 formed by the entrance of the mite — that the trace of its entrance 

 can be expected. The aperture again, does not communicate 

 with the interior of the vesicle ; it is the too close neighbourhood 

 of the little grubber that acts as the cause of the formation of the 

 vesicle; the vesicle is consequently a provision of nature to 

 protect the inner skin from the nearer approach of the cause of 

 irritation. 



The itch mite, therefore, is never situated within the vesicle, or 

 within the pustules, and there is no communication between the 

 vesicle and the burrow. 



There is no difficulty in extracting the mite from the skin ; the 

 burrow is seen without difficulty ; the end of the burrow is per- 

 ceived to be a little raised, while a greyish speck is seen beneath it. 

 As soon as this little eminence of skin is lifted, if the end of the 

 needle or pin with which the operation is performed be examined, 

 the minute, white and shining globe will probably be observed 

 attached to the instrument. If there be no such object, the point 

 of the needle placed again beneath the raised capsule of epidermis 

 will pretty certainly draw it forth. This facility of extracting the 

 little creature is due to its great power of clinging by its suckers 

 to any object with which it comes in contact. 



The proximate cause of the appearance of itch is of course the 

 presence of this mite, which is transferred by the infected to those 



