OF MICROSCOPIC OBJECTS. 13 
47H DIvIsIon. 
This includes glycerine, liquor potassee and sods, heat (as 
regards some substances), maceration (carried to incipient 
putrescence), nitric and chlor-hydric acids, either pure or 
dilute (in the case of bones, nails, &c.). 
The writer is in doubt whether glycerine ought or not to 
be included under this section or the first, its uses and 
effects being so various and interesting. Indeed, there is 
scarcely any agent to which histology is more indebted for 
its present status and progress, since there is now no doubt 
that elementary tissue can be more readily discriminated in 
this medium—perhaps, too, by it—than any other. It has 
also the valuable property of preserving the tissues, if it be 
' not too much diluted, and even then it is generally effectual 
if camphor water be employed as the diluent. The strongest 
and best glycerine should always be employed. ‘The first 
effect on tissues immersed in it is that they shrink, owing 
to the abstraction of their water; but Dr. Beale speaks in 
the highest terms of its uses and advantages, and declares 
that the tissues gradually regain their original volume if 
left in it for a sufficient time. They then soften, and even 
swellup. His practice is first to immerse the specimen in 
weak glycerine solution, and then gradually to increase the 
density of the fluid. He recommends, also, “in order that 
tissues may be uniformly permeated with a fluid within a 
very short time after the death of an animal, that the fluid 
should come quickly in contact with every part of the texture.” 
This, he says, may be effected in two ways, by 
A. Soaking very thin pieces iu the fluid; 
B. By injecting the fluid into the vessels of the animal. 
He thinks that these properties more particularly apper- 
tain to glycerine than to any other medium, and affirms 
that “ cerebral tissues, delicate nervous tissues like the retina 
or the nerve-textures of the internal ear, may be saturated 
with it, and dissection then carried to a degree of minuteness 
