PENNATULIDA. 
191 
PENNATULIDA. 
MICROSCOPIC SECTIONS AND THE MODE OF AUTOMATIC 
SECTION-CUTTING AND MOUNTING.* 
BY W. P. MARSHALL, M.I.C.E. 
The preparation of the objects for section-cutting by 
hardening, staining, and imbedding is the same as usual; 
the special points to be described are the method of cutting 
the sections and of mounting them. 
The sections are cut by an automatic machine, which 
performs the operation with great rapidity, as many as 100 
sections being cut per minute, and with such absolute 
uniformity and regularity that the successive sections as 
they are cut adhere together by their edges, following close 
after one another, so as actually to form a continuous ribbon 
of one or two feet in length. This ribbon is then divided 
into about 2J inch lengths, suitable for mounting on the 
ordinary three inch glass slides, three separate rows of the 
sections being often got upon a single slide. The special 
practical advantage arises from this, that the very large 
number of these sections, each only T (foo th or ^oo th inch 
thickness, that are required to make up a complete object, 
can be all conveniently contained upon only a few slides ; 
also all these sections are retained strictly in their correct 
consecutive order for proper examination of the structure of 
the object. In the case of the Funiculina slides now exhi¬ 
bited, there are as many as fifty separate sections on a single 
slide, and the total number of 270 sections that is required 
to complete the set of sections of a single polype from one 
extremity to the other is contained upon only six slides. 
The process of preparing an object for section-cutting is 
first to harden or toughen it sufficiently to stand the subse¬ 
quent imbedding without distortion or displacement, and 
then to imbed the object in paraffin for giving firm support 
to it during the operation of cutting the sections. 
The object is taken from the ninety per cent, alcohol in 
which it had been previously kept, and in which it can be 
safely kept any length of time till wanted for preparing, and 
is then hardened by soaking in a weak solution of picric 
acid or chromic acid, the strength of acid and time of soaking 
being varied according to the delicacy of the object. The 
object is then transferred to absolute alcohol for getting rid 
of all traces of water, and at this stage it is in most cases 
stained by hematoxylin or other reagents for the purpose of 
* Transactions of the Birmingham Natural History ancl Micro¬ 
scopical Society. Read at a Meeting of the Society. April 21st., 1885. 
