440 BULLETIN OF THE BUREAU OF FISHERIES. 



them, No. r>4. gave the highest blood pressure obtained during the wnole series of 

 experiments, namely. 120 millimeters of mercury, or Ki: J , centimeters of water. 

 The.se four fish to all external appearance seemed of equal vigor, and the pressures 

 were taken under very favorable conditions, yet the results gave practically the 

 extremes of the entire series. 



Table VI. — Showing blood pressure of four artificially spawned females taken under tht samt conditions. 



Millimeters 

 of mercury. 



No. 52, ventral aortic pressure 100 



No. 53, ventral aortic pressure 57 



No. 54, ventral aortic pressure 120 



No. 55, ventral aortic pressure 67 



The vigor of the artificially spawned females is unite apparent. They do not 

 succumb so quickly to the artificial aeration of the gills, and have more vitality on 

 the experimental table than the prime conditioned fish which, presumably, have more 

 recently arrived on the spawning grounds. 



The exhausted fish which were secured off the retaining racks gave surprising 

 blood pressures. No. 17, taken Aug. 14, 1901, was a ripe spent male, 102 centimeters 

 long. This fish gave the ventral aortic pressure of 47 millimeters, though it quickly 

 died on the table. A naturally spawned female, No. 59, taken Aug. 26, L901, gave a 

 pressure of 70 millimeters, which is almost as much as the average for all the females 

 measured. An exhausted nude taken Aug. 19. 1902, gave the stronger pressure of 94 

 millimeters for a short time, though the pressure was very irregular. 



DORSAL AORTIC BLOOD PRESSURE. 



The blood pressure measured in the ventral aorta being led off that vessel at a 

 point anterior to the first afferent branchial vessel should represent the maximal 

 pressure of the entire system. In order to determine the tall in pressure as the 

 blood flows through the gills, it is necessary to measure the pressure in some one of 

 the systemic vessels, the nearer the dorsal aortic trunk the better. Schoenlein 

 measured the pressure from the afferent branchial artery and from one of the 

 abdominal arteries in the torpedo and in sharks, and found a very decided fall in the 

 hitter as compared with the pressure measured in the first afferent branchial artery. 

 He gave the pressure in the afferent branchial artery in the torpedo as 22 to 24. in 

 no case over 30, centimeters of water (16 to 22 millimeters mercury), while in the 

 branch of the dorsal aorta and in one of the abdominal arteries the pressure was only 

 10 to 12 centimeters of water as a maximum. This great difference secured by 

 Schoenlein must have been due to the effect of the branchial resistance, which is 

 presumably high in the Selachii. 



The dorsal aorta itself was used in my experiments on the salmon. In order to 

 reach it, the tail of the salmon was cut off by a quick stroke and the arterial cannula 

 inserted into the open end of the aortic trunk. The apparatus was all carefully 

 adjusted with reference to the position of the fish before any cutting was done, and 



