4'54 BULLETIN OF THE BUREAU OF FISHERIES. 



clots would quickly stop it were it inserted. Successful pressures were finally 

 secured with a short-necked, wide-bulb, T-shaped washout cannula of the form in 

 common use in physiological laboratories and figured in Stirling's Hand-book, page 

 30K. This cannula, tilled with saturated magnesium sulphate under the proper 

 pressure to prevent the too great loss of blood into its bulb, gave tracings unob- 

 structed by clots for as much as ten minutes at a time, and clots could be easily 

 removed by taking the cannula from the artery, washing it out. and replacing it. 

 The cannula was inserted through a small puncture or slit cut in the artery with a 

 slender pointed scalpel and was held in place not by the usual ligatures hut by the 

 elasticity of the tissue around the constricted neck of the cannula. The end of the 

 cannula extended freely into the blood stream within the artery but was not large 

 enough to offer any serious obstruction to the flow of the blood stream past its point 

 of insertion. The greatest care was taken to adjust the whole apparatus with 

 reference to the position of the tish at the beginning of the experiment so that the 

 cannula should not be drawn out or the artery torn, either of which accidents was 

 almost sure to end the experiment through the foo great loss of blood. 



Measurements of the blood pressure of the dorsal aorta were made by cutting off 

 the tail and quickly inserting the cannula into the open end of this vessel, and plug- 

 ging the accompanying veins when necessary, i. e., when they were not completely 

 compressed by the cannula in the aorta. A little bleeding takes place around the cut 

 skin, but a true measurement of the pressure and its variations is obtained for a 

 period of two or three minutes and even longer. 



The blood pressure in all of the experiments reported in this paper was measured 

 by means of a Ludw r ig's mercury manometer, and the pressures are measured to the 

 maximal pressures of the heart heats. 



BLOOD PRESSURE IN SALMON FROM THE SEA. 



A vigorous effort was made during the summers of 1901 and 1902 to secure 

 measurements of blood- pressure from salmon taken directly from the sea. The 

 fishing grounds at Monterey Bay, the point visited, are so far out that it is difficult 

 to bring the tish to the shore in good condition. July 26, 1901, a single live male, 

 92 centimeters in length, was brought into the laboratory in poor condition, having 

 lost some blood from a gaff wound and being considerably asphyxiated by the trip in 

 from the fishing hanks. The blood pressure measured in the ventral aorta was found 

 to be 49 millimeters of mercury. This result can not he taken as normal, since it is 

 vitiated both by loss of blood and by insufficient aeration of the gills during the 

 experiment. It is of interest chiefly as the first attempt to make the difficult blood- 

 pressure measurement on the salmon. 



BLOOD PRESSURE IN SALMON FROM TIDE WATER. 



Black Diamond. California, at the head of Suisun Bay, just where the Sacramento 

 and San Joaquin rivers enter the bay, was visited in the first two weeks in August, 

 1902. Two live salmon, caught in nets about 3 miles distant, were brought in a small 

 float to the wharf of the Sacramento River Packers* Association, to whom we are 

 indebted for quarters as well as for many special favors facilitating our investigations. 



