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amined in "the ordinary way, and to see which you must proceed in such a way 

 as to make the nerves more opaque, but at the same time keep the tissue of the 

 cornea transparent. And what is true with respect to the cornea is true also of 

 every tissue of the body. When it is intended to introduce artificial fluids into 

 the vessels of an animal, the best way would seem to be by introducing them 

 through the channels in which the natural fluids would pass during life., and a 

 person is next led to try experiments as to the best fluid to use for the purpose, 

 and the best kind of colouring matter, and it would be found that the best fluid 

 is glycerine. Syrup would do as well in the first instance, but it decomposes, 

 and also is apt to carry with it crystals of the sugar. Glycerine, when intro- 

 duced into the large vessela of the body, readily diffuses itself into the small 

 vessels, and through their walls into the tissues, in the most complete manner. 

 In all the old preparations, and in the Ger man specimens, nothing could be 

 more beautiful than tbe appearance of the vessels ; but the structure of the 

 tissues was gone and nothing could be learnt of it. In order to make out the 

 most minute points of a texture, it must be immersed in a suitable fluid, and 

 there were some which required that an acid base, or an alkaline base — as the 

 case might be— should be mixed with the glycerine. A colouring matter must 

 also be used, and this must be perfectly suspended in the proper solution. 

 Formerly it was customary to inject with a fluid, in which was suspended an 

 opaque colouring matter, such as vermilion or red lead but the particles of 

 these pigments are frequently too large to go through the capillary vessels, and 

 this necessitated the most careful watching during the process of injection, be- 

 cause if the coloring matter was suspended in glycerine, and the pressure was 

 continued after such an obstruction had taken place, the vessels would break, 

 and the preparation would be rendered entirely useless. A finer coloring 

 matter is therefore needed for the purpose, and it was found that Prussian blue 

 was the best, as it could be obtained in a more finely divided state than any 

 other known substance ; no heat was required in its preparation, and it was so 

 fine as to remain suspended in the glycerine so perfectly as not even to require 

 shaking ; it was also inexpensive, and could be made for about Gd. per pint. 

 Everyone should make his own fluid, it was easily made from a mixture of Fer- 

 rocyanida of potassium, dissolved in water, and glycerine ; and perchloride of 

 iron, in water, and glycerine ; the one should be added to the other by degrees, 

 and the mixture shaken well each time, it was important to notice that the 

 solution of iron must be added to the Potassium, and not the potassium to the 

 iron. When made properly the solution would hold the particles of blue in 

 suspension so perfectly that they would not subside, and the strength of the 

 fluid could be easily altered by diluting it with water according to the fineness 

 of the work to be done. Dr. Beale then exhibited to the meeting some of the 

 prepared injecting fluid of good quality, and in order that members might prac- 

 tically understand the process, he asked his friend, Mr. Perrin, to prepare one 

 or two animals for the purpose of being injected before them. By proceeding 

 in the manner about to be described it was possible to inject every particle of 

 tissue, no matter what, either of the larger and higher animals, but also of 

 reptiles and others, and a perfect injection of the choroid coat of the eye could 

 be made in the course of a few minutes ; the glycerine was also a preservative 

 fluid. Many persons were sceptical as to the value of examinations of injected 

 preparations with higher powers than those obtained by a 4 m - objective, but 

 some injections were capable of beiug examined under very much higher 

 powers, the papillae of the tongue of a frog, for instance, when injected 



