II! I III I 



ctreme contraction, called calcium I 



nia\ also be shown l>\ attempting to pc ith !»'• 



serum from which the calcium has been removed Idition 



sn.liuiii oxalate which precipitates il i 



li BOOH C( ' . I'Ut ran 1 1 .nlily be made 



adding a Blight calcium chloride 



The potassium ions do nol appear, li] i I •- i ■ i n i and sodium, I 



absolutely essential for x 1 » • - tnaintenai >f tin- heartbeat; al 



heart of the turtle will beat for a long time when perfused with a solu- 

 tion containing only sodium and calcium The explanation 



lit need not, however, necessarily \»- that potassium is an u 

 constituent "t' th<' perfusion fluid, for it may well depend on the 

 there is a Bufficienl Btore of potassium 1«>.-K.-.1 .. 

 to supply the requirements of the heart mu ir tins ion for at ■ 



as long as the heat unuM continue under lircumstances In any 



- 



know that potaasium has a profound influ< 

 beat, for when the proportion of it in the perfusion fluid i* incr< 



beat I mes • ery bIov and th<- tone of the hearl i diminished 



that is, it becomes mely relaxed tho 



amounl is further increased, will verj soon come to a standstill h 



• at I \ dilated or diastolic position. 



The st riking antagonism displayed by these inorganii 

 the heartbeat has led Borne investigati • thai 



sponaible for the rhythmic activity of the heart dependa on son 

 of chemical union occurring between the inorganic cati< 



ibstani t' the heart. Union of calcium with ti 



gubstance will lead t<> Bystole 01 conl »nion i 



or potassium will lead t<> relaxation or <liast.. 



Observations on Mammalian Heart 



Investigation of the efficiency 

 I mammalian heart has shown that the p 

 must be somewhat different from that u 

 I mighl be expected, the niosl efficient pi 



in the l>l 1 serum of the particular animal v 



fused Basing his proportions upon I 



i Histitiniits of mammalian hi 



inorganic Bolution "t" the ;" • » 1 1 « * x >. • * a 



dium chloride, 9 i" Icium 



chloride, 0.042 ] ■! sodium 

 \\ ; en " I »ock lution 

 under i>r< 





