BLOOD-VESSELS IN OMENTUM OF YOUNG RABBITS. 245 



become dry, nor, I may add, come in contact with water, 

 except where that is unavoidable, as after being stained. 

 Ranvier fulfils these conditions by his process oi semi-dessica- 

 tion, for the details of which I refer the reader to his essay, 

 or the 'Traite technique d'Histologie." I adopted the fol- 

 lowing method, which I found to answer well. Two pieces 

 of mica, about an inch long and half an inch broad, are placed 

 one over the other, and a hole punched through both very 

 near one end. Small notches are made in the edges of the 

 pieces of mica before and behind the area of the holes. One 

 of the pieces should be thin. Whilst an assistant gently raises 

 the free edge of the omentum the thicker piece of mica is 

 slipped under it, and the thin piece is laid over it so as to fit 

 the under one accurately. Thus in the area of the holes in 

 the mica a portion of omentum is fixed. The pieces of mica 

 Mie held firmly together by forceps, and the omentum cut 

 round their edges with scissors. They are then tied firmly 

 together with strong thread well waxed, Avhich is fixed by the 

 notches. This done, the mica is cut across behind the pos- 

 terior ligature, the portion that previously served as a handle 

 being no longer required. 



By this procedure I obtained a portion of omentum in its 

 tialural condition, and which could not shrink, I could 

 move it from one solution to another, and by suspending it 

 in a fluid with forceps I could brush both stirfaces. Finally, 

 when I wished to mount it for examination, I laid it on a 

 large drop of glycerine, and putting another drop on the 

 upper surface, I covered the whole with a cover-glass. To 

 make the pre])avation permanent it was only necessary to run 

 Brunswick black round the edges. If the upper layer of 

 mica, with the addition of a cover-glass, is too thick to permit 

 examination with a high power, it can frequently be removed 

 without disturbing the membrane, which, after it has been 

 soaked in glycerine, has little tendency to retract. 



The time occupied in securing the omentum between the 

 mica plates is more than regained by the rapidity with which 

 all the other manipulations can be afterwards executed. The 

 preparations made in this way were more satisfactory than 

 those obtained by any other method which I tried, I owe 

 the happy suggestion of the mica plates for this purpose to 

 Mr. Ewart. 



The mica squares with their enclosed omentum were 

 treated by half and tenth per cent, solutions of osmic acid, 

 by half per cent, solution of chloride of gold, by logwood- 

 glycerine, by Miiller's fluid, and by solution of purpurine 

 according to Ranvier's formula. Those treated by Miiller's 



