164 PREPARATION AND MOUNTING 



Specimens are often taken from the frog and ike pig, as 

 being amongst the best, Goadby's Solution being generally 

 used in mounting them. The muscles of insects also show 

 the strise very perfectly. 



NERVE-TISSUE. This is seldom mounted; as Dr. Carpenter 

 observes, " no method of preserving the nerve-tissue has 

 been devised which makes it worth while to mount pre- 

 parations for the sake of displaying its minute characters," 

 but we will mention a few particulars to be observed in its 

 treatment. The nerve should be taken from the animal as 

 soon as possible after death, and laid upon a glass slide, 

 with a drop or two of serum if possible. The needles may 

 be used to clean it, but extreme delicacy is necessary. It 

 will be found that the nerve is tubular and filled with a 

 substance which is readily ejected by very slight pressure. 

 When the nerve is submitted to the action of acetic acid, 

 the outer covering, which is very thin, is considerably con- 

 tracted, whilst the inner tube is left projecting ; and thus is 

 most distinctly shown the nature of the arrangement. Dr. 

 JJockhart Clarke, who has made great researches into the 

 structure of the spinal cord, gives a part of his experience 

 as follows : He takes a perfectly fresh spinal cord and 

 submits it to the action of strong spirits of wine. This 

 gives the substance such a degree of hardness that thin 

 sections may be readily cut from it, which should be placed 

 upon a glass in a liquid consisting of three parts of spirit 

 and one of acetic acid, which renders them very distinct. 

 M. Grandry has treated nerve-tissue thus : Taking 

 portions of nervous tissue obtained from the frog and rabbit, 

 he placed them in a one-fourth per cent, solution of nitrate 

 of silver in pure water, macerating them for five days in the 

 dark, and then exposing them for three days to bright light. 

 If the surface of the cord thus treated be carefully teazed 

 out with needles, the axis-cylinders are found to exhibit a 

 very regular and sharply denned transverse striation clear, 

 unstained striae alternating with deeply tinted ones. Dr. 

 Bastian recommends us to mount delicate specimens of 



