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a needle inserted into a handle, using the left hand, then hold- 

 ing a sharp -pointed knife in the right, commence with it an 

 incision at the middle of the base of the spine, and carry it 

 through the integument down to the bone as far as its point, 

 then, with the sharp knife and needle together, reflect the 

 membrane from the upper surface of the gland, which lies in a 

 bed formed by a splitting of the integument, the bifurcation of 

 which takes place at the external edge of each gland, one layer 

 going before and another behind it ; after which they are con- 

 tinued over the spine to form its sheath. Having exposed the 

 gland itself, it should be carefully scraped out of the cavity in 

 which it lodges with the point of the knife, but the assistance 

 of the needle will be required to remove that portion which 

 occupies the grooves of the spines : it rarely happens that the 

 whole structure can be removed entire. Having placed as 

 much as can be obtained upon a slide of glass, a drop of cold 

 water is to be added, when it may be covered in with a thin 

 film of glass, and it is then ready for microscopic examination. 

 When observing the gland, the achromatic condenser should 

 be used, and a power of a quarter of an inch focus applied. 

 It then appears that there are one or more tubes, winch lie in 

 a bed of areolar tissue, into these a number of follicles open. 

 At the lower extremity of the gland, these tubes break up into 

 a great number of sacculi, which, in some instances, may be 

 seen communicating with each other. I have not been able to 

 trace the tubes to a termination at the upper part of the gland, 

 and consequently cannot say whether they open into a single 

 excretory duct or by separate orifices into the channel of the 

 spine. In addition to the glandular apparatus it must be no- 

 ticed that the whole spine is closely invested with a membrane, 

 winch may very easily be removed entire from a fresh speci- 

 men ; if it have not the resemblance to periosteum in other 

 situations, at all events it occupies the usual locality of that 

 membrane. It is made up of two kinds of cells, one large, 

 light yellow, and having oil-like contents, sometimes collected 



