138 PRACTICAL HISTOLOGY. 



CHAPTER VIII. 



THE BLOODVESSELS. 



Preparation 1. The larger bloodvessels. 

 The epithelioid lining can only be properly demon- 

 strated in fresh bloodvessels stained by nitrate of 

 silver. For this purpose a piece of a large vessel- 

 artery or vein is obtained, either from a recently - 

 killed animal or from an amputated limb, and hav- 

 ing been slit open with scissors it is pinned on to a 

 cork with the inner surface uppermost. Care must 

 be taken in doing so not to rub this surface in any 

 way. A little distilled water is then spirted over 

 the preparation from a wash-bottle, with the object 

 of removing any blood or serum that may remain 

 on the wall of the vessel, and a few drops of half 

 per cent, nitrate of silver solution are allowed to 

 flow over the surface. After a minute it is again 

 washed with distilled water, and is then put at once 

 into a beaker of spirit and placed in the sunlight. 

 After a time the surface will have acquired a gray- 

 ish tinge, with a browner patch here and there ; it 

 may now be removed from the window, but should 

 be left in spirit until the next day, when it will be 

 hard enough to enable thin sections to be made with 

 a razor from the inner surface. In order to cut them 

 it will be found convenient to remove the piece of 

 bloodvessel from the cork, and to hold it by one end 

 by the thumb and fingers of the left hand, so that 

 the piece rests by its outer surface on the ball of the 

 finger; the razor is then dipped into spirit, and as 

 thin a slice as possible (it need not be very large) is 

 removed from the inner surface of the bloodvessel 

 and placed in the spirit, after which one or two 



