164 FREPARATION AND MOUNTING 
Specimens are often taken from the frog and the pig, as 
being amongst the best, Goadby’s Solution being generally 
used in mounting them. The muscles of insects also show 
the striz very perfectly. 
NERVE-TIssvuE.—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. 
Lockhart 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 merve-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 defined transverse striation—clear, 
unstained striz alternating with deeply tinted ones. Dr. 
Bastian recommends us to mount delicate specimens of 
