VII 



MECHANICS OF THE HEART 



22: 



the changes of intrathoracic pressure, and depend on variations 

 of pressure within the right auricle. 



Many physiologists have exercised their critical and technical 

 abilities upon these phenomena of negative pulsation, the indirect 

 effects of the positive cardiac pulse and of rneiocardia. Buisson 

 (1861) was the first to describe the negative thoracic pulse, and 

 the negative pulmonary pulse ; Yoit (1865) again observed the 



FIG. 82. -Y, Pneumogram taken from the nostrils ; Co, sphygmogram from the carotids, recorded 

 simultaneously with open glottis. (Mosso.) It will be seen that the inspiratory movement 

 precedes the carotid pulse. 



rhythmical systolic inspirations, and held them to be the effect of 

 the diminution in the heart's volume ; Ceradini (1869) clearly 

 perceived the mechanical consequences of meiocardia and auxo- 

 cardia, but made no experimental study of them ; Paul Bert 

 (1870), among the oscillations of air-pressure within the trachea of 

 a dog, included those dependent on cardiac movements ; Loven 

 (1870) took tracings of the negative thoracic, and the positive pulse 

 of the radial artery, and observed them to be simultaneous ; Landois 

 (1876) obtained tracings of the cardiac oscillations of air-pressure 

 of the nasal cavities (which he termed cardio-pneumatic curves), 



FIG. S3. Co, Cardiogram taken on man at fifth intercostal space; Xa, pneumogram taken from 

 nostrils. Simultaneously recorded with open glottis. (Mosso.) 



and was the first to distinguish the negative pulse which can be 

 verified at each systole when the glottis is open, from the positive 

 pulse which occurs when the glottis is closed, and the nasal 

 cavities function as a space distinct from those of the pulmonary 

 passages, in which there is diminished pressure with each wave of 

 blood that inundates the arterial vessels. 



Mosso (1878) was, however, the first who grasped this subject 

 fully, and employed an exact experimental technique. In his cardio- 

 pneumatic curves obtained with an ordinary Marey's tambour 



