HOW TO WORK 



softest and most delicate tissues may be made to swell out almost 

 to their original volume in the densest glycerine or syrup. They 

 become more transparent, but no chemical alteration is produced, and 

 the addition of water will at any time cause the specimen to assume 

 its ordinary characters. 



1'he hardest textures, like bone and teeth, may be thoroughly 

 impregnated and preserved in strong glycerine, p. 305. Cerebral 

 tissues, delicate nervous textures like the retina, or the nerve textures 

 of the internal ear, may be permeated by the strongest glycerine, and 

 when fully saturated with it, dissection may be carried to a degree of 

 minuteness which I have found impossible in any other medium. 

 Nor is the use of glycerine and syrup confined to the tissues of man 

 and the higher animals. I have preparations from creatures of every 

 class. The smallest animalcules, tissues of entozoa, polyps, star fishes, 

 mollusks, insects, Crustacea, infusoria, various vegetable tissues, micro- 

 scopic fungi and algae of the most minute and delicate structure, as 

 well as the most delicate parts of higher vegetable tissues, may all 

 be preserved in these viscid media ; so also may be preserved the 

 slowest and most rapidly growing, the hardest and softest morbid 

 growths, as well as embryonic structures at every period of develop- 

 ment, even when in the softest state. I am, indeed, not acquainted 

 with any animal or vegetable tissues which cannot with the greatest 

 advantage be mounted thus. All that is required is, that the strength 

 of the fluid should be increased very gradually until the whole tissue is 

 thoroughly penetrated by the strongest that can be obtained. In many 

 cases the tissues may be more effectually saturated with the glycerine 

 by injection than by soaking, p. 298. Glycerine has long been in 

 use among microscopists, but my object is to show that it is uni- 

 versally applicable, that it or syrup may be made the basis of all 

 solutions employed by the microscopical observer with the greatest 

 advantage, that many points are to be demonstrated by the aid of these 

 solutions, which have hitherto escaped observation, and that there 

 are reasons for believing that very much may yet be discovered by 

 the use of these substances. 



36C. Of the Advantages of Viscid Media for the Dissection of 

 Tissues for Examination with the Highest Powers. Minute dissec- 

 tion can be carried on in these viscid media with greater facility and 

 certainty than in more limpid fluids. I can readily detach the most 

 minute parts of tissues, separate the different structures in one tex- 

 ture, without tearing or destroying them, unravel convoluted tubes, 

 and perform with ease a great variety of minute operations, which it 

 would be impossible to effect by any of the ordinary methods of dis- 

 section. With care in regulating the temperature, I can soften tex- 



