250 



Scientific Proceedings (115). 



Small doses of mercury frequently produced pronounced 

 changes in the circulation as well as respiration. One and a 

 half to two milligrams per kilo caused stimulation of respiration. 

 Frequency and particularly depth of respiration were increased 

 shortly after the administration of the salt was begun and the 

 effect sometimes persisted for several minutes after the injection 

 was discontinued. Larger doses, however, produced the opposite 

 effect. Respiration was also depressed when the injection of a 

 stimulating dose was repeated several times, thus indicating 

 cumulation. 



The effect on the circulation was more complicated. Small 

 doses usually produced a temporary rise in blood pressure of 

 about 8-10 mm. Hg, but in several experiments no change was 

 observed. When small doses were repeated so that the total 

 amount injected was 4-5 mg. of mercury per kilo, depression of 

 the circulation was observed, thus showing cumulation as in the 

 case of respiration. The changes produced usually consisted of a 

 sudden drop in blood pressure and slowing or arrest of the heart 

 which lasted in some experiments thirty seconds. This was fol- 

 lowed by recovery, the blood pressure rising rapidly and attaining 

 even a greater height than that before the injection. Very often 

 the blood pressure remained at the new high level for some time 

 and then descended again, but the descent was gradual. The sud- 

 den fall in blood pressure was a frequent occurrence, however, in 

 a number of experiments, and in a few cases no recovery took place. 



Attention may also be called in this connection to the long 

 latent period which very often preceded the sudden fall in blood 

 pressure, two to six minutes elapsing before this occurred. 



The effects on blood pressure were different when the vagi 

 were cut before the administration of mercury was begun. The 

 lowering of blood pressure was much less abrupt and longer in 

 duration. In one experiment it lasted for more than fifteen 

 minutes. Marked changes in heart action were also observed. 

 It might be added that stimulation of the peripheral end of the 

 vagus failed to elicit the usual response after a sufficient amount 

 of mercury was injected. 



