Miscellaneous . 313 



hlage, sections of bones and teeth which hare been treated with acid, 

 the fibres of the crystalline lens, &c. For the preservation of adipose 

 tissue, of the ultimate nerve-tubes, and of the blood-corpuscles, it is 

 not well adapted. Objects put up in it, after a certain time, usually 

 acquire a brownish-yellow tint. 



IV. Solution of Arsenious Acid. 

 To prepare this solution an excess of arsenious acid is boiled with 

 water, which is then filtered and diluted with twice as much water. 

 This fluid is one of the most suitable preservatives for preparations 

 from the animal kingdom ; all the tissues mentioned under the last 

 head, and also the adipose tissue, may be kept unaltered in it ; and 

 as they acquire no yellow colour, or a far slighter tinge, during their 

 immersion, I have of late years accorded a general preference to 

 the arsenical over the creosote solution. 



V. Solution of Corrosive Sublimate. 



This is prepared by dissolving one part of corrosive muriate of 

 mercury in from 200 to .500 parts of water. The strength of the 

 solution must be varied according to the nature of the object to be 

 preserved ; hence it is well, when the required degree of concentra- 

 tion is not ascertained, to put up several preparations with solutions 

 of different strengths. This procedure is especially apphcable to 

 blood-corpuscles, which can be preserved unaltered in no other fluid 

 with which I have experimented. Thus the blood-corpuscles of the 

 frog require a fluid containing ^^o*^ °^ corrosive muriate ; those of 

 birds a solution of ^^pth ; those of mammalia and man ^m^^- 



These solutions are likewise useful for keeping the elementary parts 

 of the brain, spinal cord, and retina, although all these structures, in 

 whatever fluid they are put up, undergo some alteration. Cartilage, 

 and the fibres of the crystalline lens, keep well in these fluids ; but 

 other fibrous tissues lose too much of their transparency when in 

 contact with them. They may be used, however, for preserving 

 muscular fibre, whose cross markings they render more distinct. 



For preparations of delicate vegetable tissues, and, in general, of all 

 tender organs in which it is desired to retain the starch globules and 

 chlorophyl unaltered, for freshwater Algae, Diatomacege, Confervee, 

 Infusoria belonging to the division Rotifera, &c., a solution containing 

 x^oth or 3^(jth of corrosive sublimate is the best preservative with 

 which I am acquainted. 



VI. Solution of Carbonate of Potash. 



This may be made of various strengths, with one part of the salt 

 dissolved in from 200 to 500 parts of water, and is the best material 

 for preserving the primitive nerve-tubes. Other fibrous tissues may 

 be kept tolerably well in it, but become more transparent than in the 

 fresh condition. This is sometimes advantageous, as,- for example, 

 when we wish to display the respiratory apparatus of insects with the 

 ramifications of the air-tubes. 



