burket: adrenali? un blood pressure. 221 



elements of the frog's visual field, I took pains to make the 

 following test on several occasions, both before any injection 

 had been made and also between injections. The moist cloth 

 with which the animal was kept covered, as before stated, was 

 lifted, and the eye exposed to the light of a 16-candle-power 

 electric bulb for one minute at a time. With even this strong 

 stimulation there was absolutely no change in the pressure 

 curve in any experiment. One would expect, however, to ob- 

 serve a slight change in heart action due to reflex vagus stimu- 

 lation, and in a few instances there was a slowing of one to 

 four beats per minute ; but this efi'ect was by no means a con- 

 stant result of the light stimulation. 



It was found that, because of the peculiar action of adrenalin 

 in the frog, definite results could not be obtained from injection 

 of salts and adrenalin simultaneously ; therefore this discussion 

 will deal with the separate action of these two classes of 

 substances. 



A comparison of tables I and III, pertaining to the effect of 

 salts, will show that when the doses of the different salts were 

 properly regulated, the salts under consideration had prac- 

 tically the same effect on the frog as on the cat.'* With two 

 exception.s — KCl and BaCL — equimolecular solutions were used 

 on both animals to produce these similar eflTects, the dose being 

 varied as to quantity only (0.25 c.c. for the frog and 1 c.c. for 

 the cat) ; of the two salts mentioned, a stronger solution of 

 KCl was required to bring about a depression in the frog's 

 blood-pressure, while a much weaker one of BaCL was neces- 

 sary to produce the heart stimulation and rise of pressure. 

 M/32 barium chlorid was toxic to the frog, and would quite 

 often entirely stop the heart for several seconds; M/128 BaCI. 

 had the usual tonic action. 



It was in working out the initial object of this research 

 (that of determining the vqlue of the frog's blood-pressure as 

 a means of standardizing adrenalin) that obstacles were en- 

 countered which would seem to rule out the frog as a reliable 

 animal for this kind of work. The initial dose of adrenalin 

 would always cause a considerable rise in pressure — some- 

 times as high as 12-15 mm. — but the eflFect of succeeding in- 

 jections declined rapidly till the fourth or fifth dose, which 

 would cause a change of probably 1-3 mm., this effect remain- 



3. Burket, I. B. Araer. Journal of Physiology, 1912, XXX, IV, p. 382. 

 3-Univ. Sci. Bull.. Vol. VII. No. 12. 



