50 DISSECTION *OF THE, VASCOLARES TST 2M, 
canting the excess, and finally mix the chromate held 
an suspersion tn alittle water with the plaster-of-Paris 
solution. 
The tnjection of the vessels ts best done as follows - 
Dissect off the skin and muscles from the ventral sur- 
face of the thorax. Open the thorax by cutting 
through the cartilaginous ribs at their zunctron with 
the bony rzbs on each side of the sternum from above 
the diaphragm to the third rwb, then cut transversely 
across the sternum and remove the piece of thorax 
thus zwolated. On the under side of the piece of the 
sternum left at the anterior end of the thorax run the 
two sternal arteries and veins, these must be ligated 
etther by dissecting them outand tying cach separately, 
or by passing a thread round the piece of sternum 
and binding firmly. 
Take a large cannula, to which a bet of rubber tub- 
ong 7s attached, fill wt with 0.6% solution of NaCl, 
clamp the tubing, and then insert the cannula 
ento the aorta where wt springs from the heart and 
ligature vt firmly. Fill the syringe with the 0.6% solution 
of NaCl and inject wt into the aorta, making mean- 
while a cut tn the right auricle through which the blood 
can escape. Continue the tnzection of NaCl solution 
until all the blood ts washed out. Then make the 
yellow mixture of plaster of Paris and inject ut unédl 
the artertes are thoroughly filled. If any escape takes 
place from the small arterves cut in opening the thorax, 
these artertes can castly be ligated. In this as tn all other 
enjecttons care must be taken not to let air get into 
the vessel. The rubber tubing on the cannula should be 
clamped cach time the syringe ts removed to be filled ; 
while in filling the syringe one must be careful also 
to remove all arr by holding zt tn an inverted position 
