180 PRINCIPLES OF VETERINARY SURGERY 



least resistance" that is ever ready and alvi^ays capable of 

 taking an excess of blood. Reaction, from shock is said to 

 occur from the gradual resumption of elimination of these 

 wastes. 



ETIOLOGY. — Shock is not as common in animals as in 

 man, in whom, mental emotion and a greater sensitiveness 

 of the nerves, seem to provoke attacks that animals escape, 

 owing to their relatively slight sensibility. In animals shock 

 is induced by three principal causes: (i) Physical injury; 



(2) prolonged pain or suffering that is suddenly relieved; 



(3) painful and bloody operations. 



I. Physical injury is one of the chief causes of shock. 

 When death supervenes after an injury that has not mater- 

 ially interfered with any of the vital organs, for example, 

 an extensive mutilation of a limb, shock is its cause. In ani- 

 mals only very serious injuries are capable of provoking the 

 state under consideration. Mental impression, apprehen- 

 sion of death or terror, which in man both cause and aug- 

 ment shock, play but a minor role in animals. Serious in- 

 jiu-ies are capable of abruptly arresting action of the heart 

 and respirations, of producing loss of consciousness, or of 

 depressing all of the functions for several hours. The seri- 

 ousness of shock in animals is subordinate to the character 

 of the lesion, the degree of pain, and the amount of blood 

 lost. It may rapidly terminate fatally or gradually yield to 

 the reaction of the organism. The trivial lesion is never 

 followed by shock, in the domestic animals ; it requires such 

 serious traumata as crushing of a foot, wrenching off of. a 

 hoof, extensive mutilation of the. muscles of the hip, etc., to 

 bring on the state. The writer has seen a horse die in six 

 hours after the accidental wrenching of a hoof from wedg- 

 ing, the shoe-calk on the rail of a street car track, and a dog 

 succumb to the crushing of a fore leg at the carpus after 

 suffering from shock for fourteen hours. Although a care- 



