SMALLER BLOODVESSELS. 151 



in the second place, much of the blood which 

 remains in the vessels is driven out of them. 



The brushing being completed, the loop of intes- 

 tine, with its included mesentery, is cut off, dipped 

 for a second into a capsule of distilled water, and 

 then at once placed in J per cent, nitrate of silver 

 solution. Here it is allowed to remain ten minutes ; 

 after which it is rinsed in distilled water and then 

 placed in common water in the sunlight. If the 

 day is bright, the silver is soon reduced, and all 

 that remains to be done is to place the preparation in 

 a shallow glass dish, and carefully cut off and remove 

 the piece of intestine, leaving the mesentery. This 

 must be done under water, and will require sharp 

 scissors and delicate handling, so as not to drag 

 upon the mesentery or throw it into folds. 



In order to mount it a slide is held in the water 

 and the membrane allowed to float over, after which 

 the slide is carefully lifted out with the membrane 

 flat upon it, and the excess of water is drained off. 

 Before covering it the preparation must be examined, 

 both with the unassisted eye and with a low power 

 of the microscope, so as to detect any folds or creases 

 in it. If present they can be got rid of, by gently 

 drawing out first this corner and then that with a 

 needle. A drop of strong glycerine may then be 

 placed on the middle of the preparation, and the 

 cover-glass laid on and allowed slowly to settle 

 down. More glycerine may be afterwards added at 

 the edge if necessary. Should it be found, on exam- 

 ining the preparation with a moderately high power, 

 that the outlines of the epithelioid cells of the vessels 

 are not yet sufficiently marked, it will be well to 

 leave the preparation out in the light, but covered 

 over from dust, for a day or two. 



If there is but little sunlight the reduction of the 

 silver may often be better effected by placing the 

 loop of intestine, with its attached mesentery, after 

 it has been taken from the silver solution and rinsed 

 in water, in a beaker of weak spirit (equal parts of 



