2° PREPARATION AND MOUNTING 
which he should be familiar, so as to be able to speak with 
some degree of certainty of the nature of the tissues demon- 
strated by them. 
It is now, therefore, intended to give the reader a list of 
these aids, arranging them according to the effects which it 
is desired to produce. Stricker observes, “that it is to be 
borne in mind that it is impossible to say of any fluid that 
it constitutes an indifferent, 7.e., neutral, medium for fresh 
tissues of all.kinds. In all instances we must be prepared 
for changes taking place.” He gives, however, a list of 
fluids to which structures are generally most indifferent, 7.e., 
in which least alteration may be detected under examina- 
tion while fresh, viz. :— 
1st. Fluid of the aqueous humour. 
2nd. The serum of the blood. 
3rd. Amniotic fluid, very fresh, in which a little iodine 
has been dissolved, making it of a faint yellow tint. 
4th. Very dilute solutions of neutral salts, such as: phos- 
phate and acetate of soda and potash, &c. 
It is scarcely within the power of any one observer to 
have largely used or tested the whole of the processes here- 
inafter to be mentioned. The writer therefore freely admits 
his obligations to the treatises of Drs. Beale and Carpenter, 
Mr. Quekett and Mr. Fownes, as well as to those of Stricker, 
Frey, Klein, Schultze, Kiihne, Deiters, Leber, and others, 
many of whose processes he has personally verified, and of 
whose manuals, especially those of Beale, Stricker, and Frey, 
the student is advised to possess himself. He believes also, 
from his own early experiences, that some short rationale 
of the intentions of the processes and means of investigation 
used by well-known workers may be acceptable to the stu- 
dent, in repeating their experiments before embarking in 
any of his own. 
These materials and methods may be divided, then, and 
described according to their effects somewhat as follows; 
and it ts in the judicious selection of each one or more of 
them that the tact and discretion of the student will best 
