SECTIONS OF SPINAL CORD. 701 



medulla oblongata, and spinal cord, tlie strengtli of the 

 solution may be in the proportion of one of the acid to 

 about three or even two hundred of water. It is best, 

 however, to begin with the weaker solution and increase 

 its strength at the end of some hours. If the cerebral 

 and cerebellar hemispheres be hardened in a solution of 

 greater strength, they become friable and unfit for making 

 perfect sections. "^ 



Method of Preparing Sections of the Spinal Cord. — By 

 a peculiar method of preparation, Mr. Lockhart Clarke 

 obtains beautiful sections showing the arrangement of the 

 nerve-tibres and vesicles in the spinal cord and other 

 parts of the nervous system. The results are recorded in 

 the Philosophical Transactions for 1851, Part 2. The 

 cord it appears is first hardened in acetic acid and alcohol, 

 M'hen excessively thin sections may be readily obtained 

 with a sharp knife. These are then soaked in pure spirit, 

 which permeates the texture in every part, and drives out 

 the acetic acid, and afterwards transferred to turpentine 

 ■which expels the spirit, and lastly the sections are 

 mounted in Canada balsam. By this plan the tissues of 

 the embryos of mammalian animals can also be rendered so 

 transparent that the smallest ossific points can be seen in 

 the temporary cartilages. To render the specimen more 

 transparent immerse it in alcohol to which a few drops 

 of a solution of soda have been added, and allow it to 

 remain cjiuietl}^ for a few days. When sufficiently acted 

 on, remove it, and preserve permanently in weak spirit. The 

 principle of the action of the fluid may be explained 

 thus : alcohol alone tends to coagulate albuminous textures 

 and render them opaque, at the same time that it hardens 

 them. The alkali, on the other hand, renders the tissues 

 soft and transparent, and if time were allowed, would 

 cause their complete solution. These two fluids in con- 

 junction harden the texture and at the time make it clear 

 and transparent. Many soft tissues may thus be hardened 

 sufficiently to enable us to cut very thin sections. 



Nerves may be examined in thin sections of the skin 

 after the addition of acetic acid and a solution of soda. 

 Gerber boils the skin until it becomes quite transparent, 



(1) Lockhart Clarke ou the Microscopical Examination of Nerves. 



