June 11, 1897.] 



SCIENCE. 



905 



ansesthesia has been obtained by drawing 

 blood for analysis while the animal was 

 connected with a kymograph and breathing 

 !N"jO + air or N,0 + pure oxj'gen. The 

 analysis of the blood gases shows that even 

 when the animal was so deeply anaesthe- 

 tized as to endure stimulation of a sensory 

 nerve without pain the blood contained 

 enough oxygen to support life. The COj in 

 the blood was greatly diminished. The 

 average amount of IST^O in the blood during 

 anaesthesia was 28 vols, per cent, (gas at 

 0° C. and 760 mm.) . A study of the respira- 

 tory exchange indicates that the metabo- 

 lism was lowered and that the system 

 adapted itself to the small amount of oxy- 

 gen present in the inspired air. The theory 

 frequently found in text-books that nitrous 

 oxide ansesthetizes solely by asphyxia is 

 erroneous, and the safety of nitrous oxide 

 compared with chloroform or ether merits 

 that nitrous oxide, properly mixed with 

 oxygen, be given a wider trial even in major 

 surgery. 

 On the Production of Idioventricular Rhythm in 



the Mammalian Heart. A. R. Cushny. 



The method employed was the stimula- 

 tion of the ventricle in the dog by single 

 induction shocks at a definite point in the 

 relaxation. As a general rule the ventri- 

 cular rhythm was accelerated, and both con- 

 traction and relaxation became imperfect. 

 Not infrequently, however, the ventricular 

 systole was stronger during stimulation 

 than before and afterwards, and this was 

 explained as being due to the dislocation 

 of the auriclo-ventricular rhythm. In the 

 great majority of cases the auricle assumed 

 the accelerated ventricular rhythm, and the 

 auricular systole became remarkably weak. 

 This weakness is due in part to the acceler- 

 ation of the rhythm, in part to the fact that 

 the auricle contracts while the ventricle is 

 in full contraction and has, therefore, to 

 work against much greater resistance than 

 normally. 



27(6 Cause of the Heart Beat. W. T. Poeter. 



Any part of the dog's ventricle, even the 

 apical fourth, will contract rhj'thmically, 

 when cut away from the remainder of the 

 ventricle and fed with warmed, defibrinated 

 dog's blood through a cannula placed in the 

 coronary artery ramifying in the extirpated 

 part. Hence: (1) the cause of the rhythmic 

 contraction of the ventricle lies within the 

 ventricle itself; (2) the cause of the rhyth- 

 mic contraction is not in a single localized 

 coordination center; (3) the coordination 

 mechanism, whatever it may be, is present 

 in all parts of the ventricle ; (4) the integ- 

 rity of the whole ventricle is not essential 

 to the coordinated contraction of a part 

 of the ventricle ; (5) assuming the correct- 

 ness of the general belief in the absence of 

 nerve cells from the apical half of the ventri- 

 cle, the rhythmic coordinated contraction of 

 the ventricle is not dependent on nerve cells. 



A thin piece of the beating ventricle of 

 the dog's heart in situ in the living animal 

 may be partly severed from the apical por- 

 tion in such a way that the isolated piece 

 remains attached to the remainder of the 

 ventricle only by its nutrient vessels, all 

 muscular connections being cut. The heart 

 and the isolated piece continue to contract. 

 On slowing the heart by vagus excitation, 

 the rhythmical contractions of the isolated 

 piece may be watched without difficulty. 

 Their rhythm then differs from that of the 

 remainder of the heart. It follows that the 

 rhythmic contractions of th e isolated mam- 

 malian apex are not due to changes in the 

 blood during its defibrination. 

 Tlie Recovery of the Mammalian Heart from 



Fibrillary Contractions. W. T. Porter. 



Recovery of the dog's heart, or of any 

 isolated part of it, from strong fibrillation 

 produced either by electrical stimulation, 

 mechanical insult, or sudden deprivation 

 of blood supply, is secured by feeding the 

 part with defibrinated dog's blood through 

 its coronary artery. 



