WITH THE MICROSCOPE. 299 



of the most delicate tissues, or interfering with the demonstration of 

 their ultimate structure. 



The Preparation of Specimens. 



376. The Practical Operation of Preparing Tissues for Exami- 

 nation with the Highest Powers. The general plan I follow, is the 

 same for all tissues of all vertebrate animals and morbid growths ; 

 but I will describe the several steps of the process as they are 

 conducted in the demonstration of the structure of the ganglion 

 cells, described in my paper in the Phil. Trans, for 1863, and 

 of the papilla of the frog's tongue, described in the communica- 

 tion presented to the Royal Society in June, 1864. The figures 

 in plates XLIII, LXVII, and XLVIII, have been taken from these 

 memoirs. 



The description given also applies to the mode of preparing 

 specimens of muscular fibre to demonstrate the mode of distri- 

 bution of the finest branches of nerve fibre.* See plates XXVIII, 

 LIX, LX, LXI, and LXIL It is the same plan which I have 

 followed in the investigation of the minute structure of the brain, 

 spinal cord, and ganglia of man and the higher animals, f 



My researches upon the tissues of the frog have been principally 

 conducted upon the little green tree frog (Hyla arborea), for 

 experience has proved to me that the tissues of this little animal 

 are so much more favourable for investigation than those of the 

 common frog, that it is well worth while to obtain specimens, even 

 at the cost of 2s. or 2s. 6d. each. 



The frog is killed by being dashed suddenly upon the floor, but 

 it must first be carefully folded up in the centre of a large cloth, 

 so that the tissues may not be bruised in the least degree. Next, an 

 opening is made in the sternum, the heart exposed, and a fine 

 injecting pipe, after being filled with a little injection, is tied in 



* ' On the distribution of nerves to the elementary fibres of striped muscle.' 

 Phil. Trans., 1 860. 



' Further observations. ' Phil. Trans., 1862. 



' Further observations in favour of the view that nerve fibres never end in 

 voluntary muscles.' Proceedings of the Royal Society, June 5th, 1863. 



' On the structure of the sarcolemma of the muscular fibres of insects, and of 

 the exact relation of the nerves and tracheae to the contractile tissue of muscle. ' 

 Microscopical Society, June, 1864. 



t ' On the minute structure of the grey matter of the convolutions of the brain. ' 

 Proceedings of the Royal Society, vol. XII, 671, 1863. 



' Indications of the paths taken by the nerve currents as they traverse the 

 caudate nerve cells of the spinal cord and encephalon.' Proceedings of the 

 Royal Society, July, 1864. 



