126 Surgical Diseases and Surgery of the Dog 



other factors, and that even with fatal outcome death may be de- 

 layed to the extent of several hours. Between five and ten per 

 cent of all heart wounds terminate in recovery. It is known, how- 

 ever, that there is a spot in the septum, between the ventricles, 

 where simple puncture with a fine needle is followed by immediate 

 arrest of cardiac action. In other respects, when a heart wound 

 proves fatal it depends upon either of two factors, viz., acute 

 hemorrhage or intracardial pressure. In either case the same re- 

 sult ensues, viz., starvation of the organ. In the former case 

 the wound in the pericardium is sufficient to allow the escaping 

 blood to pass out through the external wound or into the pleural 

 sacs in such quantity that it no longer enters the organ in sufficient 

 volume to stimulate the muscle of the latter to contract. In the 

 latter case the rent in the pericardial sac becoming sealed from one 

 cause or another, the accumulating blood reacts on the organ by 

 compression. Cohnheim has shown this by injecting various quan- 

 tities ©f fluids into the pericardial sac, the pressure being mainly 

 sustained by the auricles and great vessels at the base of the heart. 

 The ventricles continue to contract, but the auricles and great ves- 

 sels being compressed the entry of blood gradually decreases until 

 the heart pumps itself dry, and finally the ventricles also cease. 



Wounds may be penetrating or non-penetrating, but the hem- 

 orrhage from the former is usually more copious than from the latter, 

 though from the latter a hemorrhage may be as serious in its re- 

 sults as from the former. The hemorrhage usually takes place 

 during systole, but it may also occur during diastole when the 

 wound is very large. Wounds of the right ventricle bleed more 

 freely than do those of equal size in the left, the latter closing 

 by coagulation more rapidly than the former, owing to the greater 

 length of the wound canal and thickness of the wall. For the same 

 reason perpendicular penetrating wounds bleed more freely than 

 do oblique. Hemorrhage is more severe in wounds from sharp 

 instruments than from bullets. When a penetrating body plugs 

 the wound, so to speak, a fatal outcome may be averted, or at least 

 delayed, some hours. In Nocard's clinic at Alfort a dog was re- 

 ceived whose heart was transpierced by an arrow. Its master had 

 endeavored to extract the missile, but the latter had broken off 

 short in the wound. The animal had then run for miles, and did 

 not succumb until the following day, Nocard remarked that had 



