Intraventricular and Aortic Prn.ssure (Jnrvcs. 435 



Description of plate XX. 



All Figures to be read from left to right. Time tracing (when present; in 



tiftieths of a second. In all, (except Fig. 10), the lower edge of the meniscus was 



focussed, so that the curve to be read is formed by tlie line of junction of the 



lowest white area with the middle grey or black area. 



Pig. 1. Test of instrument. Deflection caused by suddenly diminishing pressure 

 from 95 mm of mercury to zero. Shows absence of vibrations with a rate 

 of alternation of pressure at least as steep as that of the intraventricular 

 pressure. The faint vertical lines, (caused by slight regular variations 

 of velocity of the photographic film), serve as convenient ordinales to 

 measure from. 



Fig. 2. Intraventricular pressure of left ventricle. Heart beating quickly. Plateau 

 with three waves on the top, second, and third waves partially fused. 



Fig. 3. A similar curve from another dog, heart beating rather more slowly, second 

 wave higher than the first. 



Figs. 4 and 5. Intraventricular pressure of left ventricle. Vagus excited. Shows 

 auricular beat, the three waves on the summit of the plateau, the wave 

 on the descent, and considerable negative pressure following the ven- 

 tricular beat. The beat after the negative pressure in Fig. 4 is apparently 

 an auricular beat not followed by a ventricular beat, owing to the vagus 

 excitation. In Fig. 5, there are also some isolated auricular beats. 



Fig. 6. A similar curve from another dog. Heart beating slowly from morphia. 

 Shows very distinctly the three waves on the summit of the plateau and 

 the notch on the descent. 



Figs. 7, 8 and 9. Various forms of katacrotic, aortic pressure curves. In Fig. 7, 

 vagus excited. All show three waves (corresponding to the three waves 

 on the plateau of the ventricualr curve) preceding the dicrotic notch and 

 two waves following it. 



Fig. 10. An anacrotic aortic pressure curve. In this case the top of the meniscus 

 was focussed, so that the curve to be read is the junction of the grey 

 area with the white strip between it and the uppermost lighter grey area. 

 (An unusual form.) 



Note. Figs. 7 and 8 come from the same dog as Fig. 2, and Fig. 9 from 

 the same dog as Figs. 3, 4 and 5, Figs. 6 and 10 come from two other dogs. 



28* 



