CONTRIBUTIONS FROM THE ZOÓLOGICAL LABORATORY OF 
THE MUSEUM OF COMPARATIVE ZOÓLOGY AT HAR- 
VARD COLLEGE. E. L. MARK, Director. No. 165. 
POSTERIOR CONNECTIONS OF THE LATERAL 
VEIN OF THE SKATE. 
HERBERT W. RAND AND JOHN L. ULRICH. 
FoR several years the senior author has used the skate to 
illustrate to classes in the comparative anatomy of vertebrates 
the main features of the primitive circulatory system of verte- 
brates. The injection of the systemic veins of the skate is 
attended with more or less difficulty, especially at the hands 
of students of little experience, and even under the most favor- 
able circumstances it is difficult, if not impossible, to secure a 
complete injection of the veins by the methods ordinarily pre- 
scribed (see, for example, T. J. Parker, '95, pp. 48-49). The 
difficulty lies partly in the fact that 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 in 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. Although 
a large number of injected skates had come under observation 
in the laboratory, the relations of certain of the veins in the 
region of the kidneys had never been clearly demonstrated. 
The veins of certain foreign species of skate have been well 
described, notably by T. J. Parker ('81). Conditions similar to 
those found in foreign skates are to be expected in our local 
species. Nevertheless, it seemed to the authors to be worth 
while to determine precisely the condition of the vessels whose 
connections were in doubt, especially in view of the fact that 
there was strong evidence of one striking difference between our 
common skate and the species described by Parker, in the pos- 
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