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a very short time. When it is put in carbonic acid gas, its beat- 

 ings are, at first, increased in frequency and strength ; but they 

 very soon are stopped. When it is put in oxygen, its beatings 

 are slowly increased in frequency and strength, and they last 

 very long. 



i. On newly-born cats and dogs, before the occlusion of the 

 ductus jarteriosus, I open the chest and put a ligature on the ar- 

 teries going to the head and fore limbs, and on the aorta imme- 

 diately after the origin of the ductus arteriosus. Then the blood, 

 expelled from the right ventricle, is sent to the lungs, from which 

 it comes to the left auricle, and afterwards to the left ventricle. 

 From there it is sent into the only part of the aorta remaining ac- 

 cessible, and thence it goes into the cardiac arteries, and into the 

 pulmonary artery, through the ductus arteriosus, (a direction which 

 is the reverse of the normal direction in that duct.) By the cardiac 

 veins the blood arrives again in the right side of the heart. The 

 circulation from the heart to the lungs, and vice versa, continues 

 very well. I have found, that if hydrogen is insufflated into the 

 lungs, the beatings of the heart are not much changed at first, 

 but they go on diminishing, and they disappear in a short time. 

 When an injection is made with carbonic acid, the beatings of the 

 heart are quickly increased in frequency and strength ; but they 

 are stopped after a short time. When oxygen is insufflated, the 

 beatings of the heart become slowly more frequent, and they re- 

 main quick and strong for a long time. (I have once, by such 

 insufflation of oxygen, maintained beating for eleven hours in the 

 heart of a young cat.) 



I believe that these facts prove that black blood, by its car- 

 bonic acid, is an excitant of the beatings of the heart. If, now, 

 we adduce to these facts all those I have related in a preceding 

 article, on the apparently spontaneous contractions in all the 

 contractile tissues of the body, we shall have a very considerable 

 number of facts, proving that, during asphyxia, there is an ac- 

 cumulation in the blood of the principle which causes these con- 

 tractions. I believe that it is almost impossible to deny that this 

 principle is the carbonic acid gas- 

 Before trying to show that what takes place in asphyxia in 

 the heart is only an exaggeration of what normally exists in that 

 organ, I will treat the two remaining of the three questions I 



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