OF MICROSCOPIC OBJECTS. 1$ 



4iH DIVISION. 



This includes glycerine, liquor potassae and sodse, 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; bub 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 

 swell up. His practice is first to immerse the specimen in 

 weak glycerine solution, and then gradually to increase th& 

 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 in 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 



