230 ON THE CIRCULATION IN THE SNAPPING TURTLE. 
m.m. in one case and to 14 m.m. in another. Pulse 29. The carotid artery at this time 
exhibited a pressure of from 41 to 53 m.m. 
ExprriMent.—Turtle. Weight 20 lbs. The tube having been placed in the distal end 
of the vessel, the column rose to 5 m.m. Slight pulsation of to 2mm. During mus- 
cular action it rose to 28m.m. Pulse 36. ‘The tube was next placed in the cardiac end 
of the cut vein, when it rose to 3 m.m. and pulsated about 13 m.m. Similar results were 
obtained upon further experiment. When the tube was placed in the distal end of a 
large vein, the average height of column of mercury supported was 6.7 m.m. In the 
cardiac end of the same veins the average was 3 m.m. In all cases muscular motion 
elevated the column from 11 to 30 m.m. 
It will be seen above that a pulsation of feeble character took place even when the 
distal end of the vein was examined. This singular phenomenon appears to be a normal 
occurrence in the larger veins of the neck. In those of the limbs it was scarcely per- 
ceptible, but in the neck it was always visible, and was well marked in the great veins, 
and best of all in the external jugular. At first I supposed it to be due to the pulsation 
of neighboring arteries, or to the transmission through anastomotic channels of the pulse 
which is noticed when the lower or cardiac end of a vein is the subject of study. The 
first of these possibilities is negatived by the fact that the pulsation was still seen where 
the vein chosen was remote from any large artery, which is the case with the external 
jugular vein. The second is disposed of by making use of the dorsal vein or external 
jugular far up in the neck, and where it is thus remote from large communicating 
branches. 
The pulsation referred to is, in all probability, due to the propagation of the heart-force 
through the capillary system into the veins. ‘The venous pulse which was observed in the 
cardiac end of the veins of the neck, was not visible in the veins of the limbs. It was 
due, no doubt, to the pulsatile action of the walls of the vena cava, so well described 
by Alison. 
Muscular movements, as in other animals, increased the venous pressure considerably. 
The influence of the respiratory acts on the venous circulation was imperfectly studied, 
owing to a failure of proper material, and is, therefore, reserved for future study. 
