THE SKIN. 187 



one or two of the thinnest should be mounted in 

 glycerine as soon as cut, without staining, merely 

 placing them first in water, to remove the spirit. 

 The fibrous-looking tactile corpuscles can generally 

 be made out better in these than in the preparations 

 which have been mounted in dammar. 



Preparation 7. To show the arrangement of the 

 bloodvessels, sections of skin from a limb which has 

 been minutely injected may be. made and mounted 

 in dammar by the usual process. These must either 

 be left entirely unstained or the staining must be 

 very slight indeed. These sections will generally 

 include clusters of fat-cells, with their vessels. 



Preparation 8. The following method will serve for 

 the demonstration of some points in the structure of the 

 corium, as well as the arrangement of the bloodvessels. 1 

 One of the limbs of an animal, preferably of a dog, is in- 

 jected with a solution of Berlin blue, the injecting canula 

 being- placed in the principal artery of the leg, and a band 

 being tightened firmly over the upper part of the limb 

 after the injection has been flowing for a minute or two, 

 so as to compress everything except that vessel and pre- 

 vent the further escape of the injection from the veins of 

 the limb. A pressure of from four to eight inches of mer- 

 cury is then maintained for several hours. In this way 

 all the vessels become completely distended with the blue 

 fluid, the watery part of which in large measure exudes, 

 so as to render all the tissues cedematous. If colored 

 gelatine is employed the limb is all the while kept 

 thoroughly warm by placing it over a large water-bath 

 and covering it with a glass plate or bell-jar; and the 

 gelatine in the injecting-bottle and supply-tube must also 

 be kept fluid by similar means. After the time mentioned 

 the artery may be tied and the limb, if gelatine has been 

 employed, removed to a cool place. When it is considered 

 that the gelatine is entirely set, a piece of the skin is cut 

 out, stretched over a dialyzing glass and placed in a 

 beaker of digestive fluid, which has been previously pre- 

 pared by adding a few drops of a glycerine extract of the 



1 W. Stirling in "Journal of Anatomy and Physiology," vol. 

 x. pp. 185 and 465. 



