If exudate is present in considerable quantities a liquid sound is heard at each heart beat. The heart appears to be beating in water, but the liquid note varies considerably. It has been termed the “claclaque” sound (Lecouturier, 1846), in allusion to the sound produced by the meeting of water ripples; “clapotement” sound (Boizy, 1858), with reference to the sound produced under the influence of a light breeze on the borders of a stream; “glou-glou” sound (Roy, 1875), suggested by the noise of liquid escaping from an inverted bottle into a resonant vessel, etc. It is important, however, to remember that cases occur (principally when the pericardium is greatly distended and entirely filled with liquid) where, with the animal at rest, these sounds are difficult to detect. To render them noticeable the patient must be walked for a few yards.
Vernant, again, has described a sound as of dripping water, of quite special character; he compared it to that resulting from the fall of drops of liquid on to a marble table or into a half-filled vessel. So far as can be ascertained this sound of dripping water greatly resembles that heard in pneumo-thorax, but it is less resonant and less prolonged.
It appears to be characteristic of the presence of air in the pericardial cavity, and its special quality varies with the quantity accumulated in the pericardium. Masked by these pericardial sounds the beating of the heart seems dull, badly defined, distant and stifled.
Fig. 175.—Appearance of a patient suffering from fully-developed pericarditis.
B. Jugular symptoms. The “jugular” symptoms are secondary, and result from the accumulation of liquid in the pericardial cavity. No intra-pericardial exudate can exist without exerting pressure on the heart, and as the auricles have very thin walls and are more compressible than the ventricles, this pressure immediately causes difficulty in the return circulation, whence venous stasis, varying in intensity, but clearly visible and appreciable on account of the distension of the jugulars.
The venous stasis is general, for the pulmonary veins are as much compressed as the posterior and anterior venæ cavæ, but it is only apparent in the large superficial veins. This stasis is accompanied by venous pulse, and particularly by peripheral or internal œdema, œdema of the lung, intestine, mesentery, etc., of the submaxillary space and of the dewlap and entrance to the chest. Œdema of the submaxillary space is specially characteristic, for it appears almost first amongst external signs. That of the dewlap follows at a later stage, and extends backwards as far as the umbilicus, rising above this point as high even as the entrance to the chest and the axillary region.
C. Pulmonary symptoms. The pulmonary symptoms result from difficulty in the return circulation and from the venous stasis. They are due to passive congestion and œdema of the lung or to hydro-thorax. At rest the respiration may appear fairly regular, but at the least movement it is accelerated, and may rise to 40 or even 60 per minute.
Percussion reveals lessened resonance of the parts, and in the case of hydro-thorax dulness marginated by a horizontal line, as in pleurisy.
On auscultation the vesicular murmur may sometimes have diminished or even disappeared, while the respiration may be blowing, as in active congestion, and in exceptional cases a tubal souffle may be observed. In most cases the animal has a paroxysmal, somewhat frequent cough, due to reflex irritability of the pneumo-gastric.