e. Rupture of Abscess into the Peritoneum. As an abscess is nearly always the product of pus microbes it follows that its rupture into the abdominal cavity will determine infection. If the abscess contains some special infective germ like that of strangles or glanders the resulting inflammation partakes of their nature.
f. Penetration of Microbes through the Circulation. Healthy blood is free from germs, yet it is not uncommon to find a few circulating in the blood in given conditions. Debility, toxin and ptomaine poisoning and other conditions render it possible for bacteria to successfully invade the circulating blood, hence, many infective diseases are at first local, and later on become generalized. Under these circumstances any cause of debility operating especially on the peritoneum opens the door to their infection. Under such debilitating causes all those already referred to as chills must be recognized, together with kicks, blows, local congestions and other injuries.
Symptoms. The existence of a penetrating wound or sore of the abdomen, a kick, an open abscess, or a recent exposure to severe cold when heated and fatigued, or finally some serious affection of the abdominal organs will give definiteness to some of the symptoms which follow. There may have been noticed a rigor, or trembling of the muscles may still continue. There is swelling around the external wound, which in case of castration is usually œdematous and more or less tense, affecting the entire sheath and extending forward on the abdomen. In any such case there is tenderness to pressure around the margin of the wound, for a distance that constantly increases. The animal moves stiffly and the back is more or less arched. The temperature is raised two or three degrees and may go on till it has reached 107. The patient becomes dull and listless, with drooping head and ears, sunken, lustreless, pale eye, more or less fixed, lips drawn up firmly and muscles of the face contracted and prominent. He stands with back arched, loins insensible to pinching, and legs drawn somewhat toward each other under the belly. There are indications of colic, pawing, looking toward the flanks, and shifting of the hind feet without the violent kicking motion of spasmodic colic or intestinal congestion. When he lies down it is comparatively slowly and carefully and he is more inclined to lie on the side with hind legs, or at least the one on the affected side extended backward. The rolling on the back and the sudden jerking movement of the hind limbs, seen in spasmodic colic are rarely noticed. There are exceptions to this rule when violent spasms or acute congestion is present as well as in some cases following castration and with strangulated cord.
The abdominal walls are always tense from muscular contraction, and often also from tympany, in which case there is marked drumlike resonance, on percussion. An elevated ridge like that seen in pleurisy extends from the outer angle of the ilium to the lower end of the last rib. The breathing is hurried and carried on mainly by the ribs, the diaphragm being kept as fixed as possible. The inspirations are short and catching as in pleurisy, the expirations a little more prolonged. In standing the hind legs are held apart, and in moving the animal straddles and moves them stiffly avoiding advancing them far forward. Constipation is the rule the rectum containing a number of small, round, dry balls, yet after a day or two diarrhœa may set in. Urine is usually suppressed, or passed in small amount and of a high color. The pulse is usually small, hard, and at times thready, the skin perspires more or less generally, prostration and dullness set in and death may occur within 24 hours or more commonly in 4 to 8 days. After the 1st day there may be fluctuation of the abdomen from liquid effusion.
In case of infection from perforated or ruptured stomach or intestine the symptoms are more severe from the first, and the issue is more rapidly fatal. With marked trembling, there occur extreme weakness and prostration, dull, sunken eyes, flaccid facial muscles, cold perspiration, chilly ears and limbs, entire cessation of defecation, small, weak accelerated pulse, breathing rapid, broken in inspiration or expiration, and more or less tympany. Yet the tenderness of the abdomen is less marked, and the animal may move with somewhat less stiffness, and gets up and down with less apparent suffering. The temperature is less elevated than in the external traumatism, and the whole aspect is that of collapse and sinking. These cases may die from shock or tympany in a few hours, or they may survive 24 or even as long as 48 hours but rarely longer. In case of rupture of the stomach there may be the usual feature of eructation or vomiting. Resolution may occur but non-fatal cases are liable to become chronic with ascites.
Diagnosis. Apart from traumatism, the evidence of some previous intestinal or gastric lesion, or abscess, succeeded by continuous dull colicy pains, the arching of the back and drawing together of the limbs, the tender abdomen, the careful decubitus and lying on the side, the tympany, obstinate constipation, and pale conjunctiva, the pleuritic ridge and breathing without the friction sounds or intercostal tenderness of pleurisy, the high temperature, the weak rapid pulse and rapidly advancing weakness, prostration and collapse furnish a combination which is very characteristic.
Lesions. In rapidly fatal cases there may appear to be little more than general peritoneal congestion and ecchymosis. In such cases, however, there is usually a mixture of the ingesta with the intestinal convolutions and omentum.
In cases that have survived twelve hours, false membranes are found, in the form of fine filamentous shreds on the surface of the congested serosa, which has become dull, opaque, and thickened. In twenty-four to thirty hours these have increased in thickness and solidity, binding together the convolutions of the intestines or floating free as shreds or membranous layers in the exuded liquid. At first yellowish white, these become gray, red, and finally white as they become organized into fibrous tissue. They may cover any of the abdominal organs and bind these together more or less firmly.
The liquid effusion collecting at the lower part of the abdomen, may be blood red, serosanguinolent, or straw colored, and contains a considerable amount of albumen, fibrine, granules and cells as well as the bacteria. It may attain to as much as 25 or 30 quarts. When purulent or septic the liquid is comparatively limited in amount and is usually connected with a ruptured abscess or external wound or intestinal perforation. The presence of alimentary matters, the fœtid odor, and gaseous emanations are marked features in this last condition.
The intestines are usually distended with gas, and have thin walls infiltrated, pale and thickened, and often bound to other convolutions or to adjacent organs by false membranes. The liver and spleen are pallid, and their capsules swollen, thick and opaque, with more or less membranous exudate.