376 THE AMERICAN NATURALIST.  [Vor. XXXIX. 
through the arterial cone, as directed by Parker ('95, p. 48). 
For the systemic arteries, Parker makes a single injection at the 
duodenal artery. But, unless one is dealing with a large skate, 
I have found it better to inject the anterior mesenteric artery 
(see Fig. 1), in spite of the fact that it is necessary to inject it 
backward (to secure an injection upon the intestine) as well as 
forward. The greater size of the anterior mesenteric artery and 
its accessibility, lying, as it does, along the very edge of the 
mesentery, are advantages which more than offset the necessity 
of injecting it both ways. As for details, such as the form of 
the cannula and the manner of inserting it, I should consider 
Parker's method applicable to a very large fish only. The cali- 
ber of the anterior mesenteric artery in skates of small or 
medium size is such as to require the use of a cannula with a 
slender slightly tapering tip. By Parker's method, a cannula- 
full of air is injected into the vessel. To avoid this, the cannula 
should be attached to the syringe and filled with the fluid before 
being inserted into the vessel. 
In the accompanying figure of the skate I have indicated the 
points at which the injections may best be made, to secure as 
nearly as possible a complete injection of the blood vessels in 
three colors. The mesenteric vessels are conveniently reached 
by turning the stomach forward (so that, as the fish is viewed 
from the ventral side, the dorsal aspect of the stomach is seen) 
and pulling the digestive tube over to the animal's right side in 
such a way as to stretch out flat the mesentery. The figure 
represents the digestive tube in this position. 
The several injections may well be made according to the 
following plan. Whatever the order, the arteries should be 
injected before the veins. 
ARTERIES. 
I. Arterial cone - -- --- forward - - - blue starch- pmp or Tagin 
2. Anterior mesenteric forward - - - red 
3. “ tt backward en © t « “ 
VEINS. 
Hepatic Portal. 
4. Mesenteric --...... forward - - - salen March gelain o ud Manet 
MU CS E EKAE backward - 
