No. 462] THE SKATE FOR ANATOMICAL STUDY. 369 
given an opportunity for observing, in an appreciative way, a 
remarkable case of modification of form. If the student’s main 
work is on the skate, he should at least be given an opportunity 
to compare skate and dogfish far enough to make clear to him 
the character of the skate's departure from the more primitive 
conditions. 
INJECTION METHODS. 
Injection of the Veins of the Skate— What I have to say 
about the injection of the veins of the skate is with special refer- 
ence to the best method by which this operation may be per- 
formed by students who have had little or no experience in such 
work. It is assumed that the injecting is to be done by means 
of an ordinary hand syringe. 
A complete injection of the systemic veins of the skate is 
difficult to obtain, even under the most favorable circumstances, 
partly because the veins are well provided with valves which 
impede the flow of the injection mass in a direction the reverse 
of that of the blood-flow, and partly because of the presence 
of large thin-walled sinuses, which are likely to rupture before 
the injection. mass can be forced into the smaller vessels and 
those more remote from the point of injection. 
The vessels most accessible for the injection of the systemic 
veins are the postcardinal veins in their renal region, the venous 
sinus, and the lateral veins. Parker ('95) recommends intro- 
ducing the injection mass at the venous sinus, the flow of the 
mass being directed backwards, or away from the heart. An 
injection directed forward into the hinder or renal part of one 
of the postcardinal veins has been employed with more or less 
success. In my opinion, however, injection by way of one of 
the lateral veins possesses certain advantages Over either of the 
other methods. : Bo 
The injection of the renal division of the postcardinal vein is 
objectionable for two reasons. In the first place, it is very dif- 
ficult to dissect out the vessel. It lies under the peritoneum in 
a loose mass of connective tissue, and unless the operator is 
fairly skillful, the cannula is quite likely to be, pushed into lymph 
