INJECTED PREPARATIONS 



-CAPILLARY VESSELS. 



745 



with very slight pressure ; the Ammonia having a tendency to 

 soften the walls of the vessels. When they are fully distended, 

 the preparation is to be left for from 12 to 24 hours, in order that 

 time maybe allowed for the Carmine liquid which has permeated 

 the Capillaries, to soak through the different tissues and stain the 

 germinal matters fully. Next a little pure Glycerine is to be in- 

 jected, to get rid of the Carmine liquid ; and the Prussian Blue 

 fluid is then to be injected with the utmost care. When the 

 vessels have been fully distended, the injected preparation is to be 

 divided into very small pieces ; and these are to be soaked for an 

 hour or two in a mixture of 2 parts of Glycerine and 1 of Water, 

 and then for three or four. days in strong Glycerine acidulated 

 with Acetic Acid (5 drops to 1 oz.). Preparations thus made are 

 best mounted in Glycerine Jelly ; and may then be examined with 

 the highest powers of the Microscope. 



581. A well-injected preparation should have its vessels com- 

 pletely filled through every part ; the particles of the colouring 

 matter should be so closely compacted together, that they should 

 not be distinguishable unless carefully looked-for ; and there should 

 be no patches of pale uninjected tissue. Still, although the beauty 

 of a specimen as a Microscopic object is much impaired by a defi- 

 ciency in the filling of its vessels, yet to the Anatomist the dispo- 

 sition of the vessels will be as apparent when they are only filled 

 in part, as it is when they are fully distended ; and imperfectly 

 injected Capillaries may often be better seen in thin sections 

 mounted as Transparent objects, than such as have been completely 

 filled. 



582. A relation may generally be traced'between the disposition 

 of the Capillary Vessels, and the functions they are destined to sub- 

 serve ; but that relation is obviously (so to speak) of a mechanical 

 kind ; the arrangement of the vessels not in any way determining 

 the function, but merely administering to it, like the arrange- 

 ment of water or gas-pipes in a manufactory. Thus in Fig. 395 

 we see that the Capillaries of Adipose substance are disposed in a 



Fig. 395. 



Fig. 396. 



Capillary network around Fat-cells. 



Capillary netwox-k of Muscle. 



