Method of Study. 
829 
the wall of the pericardial chamber from collapsing and pressing 
the soft heart out of shape. 
After fixation, the heart should be carefully removed, cutting 
the arteries which arise from it as long as possible, passed 
through alcohols of gradually increasing strength, and the hard¬ 
ening completed in 95 per cent, alcohol. As soon as this is 
accomplished (four to six days), the heart may be stained in any 
of the usual stains, embedded in paraffin and sectioned serially. 
Oareful attention should be given to the dehydration, as I have 
found that it takes place quite slowly. 
The sections used for study were cut .02 mm. thick, and at 
right angles to the long axis of the heart. 
In order that the form and relation of the various parts of 
the heart might be easily grasped, use was made of Born’s 
method of reconstruction of objects from serial sections. 3 
The wax plates were prepared by melting together four parts 
of best yellow bees-wax and one part resin, and pouring the 
liquid mass on the surface of hot water contained in a tank of 
given dimensions; when cool, this gave a plate of uniform thick¬ 
ness. Plates made by this formula I found much superior to 
those obtained from the dealers. 
After the drawing on the plates was completed and the proper 
parts cut out, the plates that were to enter into the reconstruc¬ 
tion were fitted together, and the whole fused by means of a 
Iiot tool; when this was accomplished, the model was cut into 
three parts. The cavity of the heart was treated in a similar 
manner to the outer surface. 
As a control of the model, outline drawings of the heart pre¬ 
vious to sectioning, as well as drawings of other hearts, were 
used. 
A complete study of the vascular system was not made. The 
large arteries were followed sufficiently far to show their course 
and general distribution. 
The vascular system may be studied by injecting the vessels 
with a solution of soluble Prussian blue in distilled water. The 
injection may be accomplished by inserting the needle of a 
3 Die Plattenmodellirmethode, Archiv f. mik. Anat., 1883, and Zeit f. 
wiss. Mik., 1888. 
