The pale, watery condition of the blood was recognized as one of the most constant features in 1868, together with the disappearance of the red globules. The clot is remarkably soft and, at the crisis of the disease, the serum is of a reddish hue by reason of the hæmoglobin in solution. When, however, the urine is no longer stained, the hæmoglobin having been eliminated, the serum assumes its normal pale amber hue. For the first counting of the red globules in this disease we are indebted to the Bureau of Animal Industry. The average count in healthy cattle approximated to 6,000,000 per mm. of blood, and in three days this would descend to 4,000,000, 3,000,000, 2,000,000 or even 1,183,000. The rates of decrease was ⅛ to ⅙ of the entire number in one day. In case of recovery the repair of the red globules was slow, from one to two months being required to bring them up to the normal standard. Lignieres claims recoveries after the count had gone as low as 300,000 per mm., and in fatal cases, a few hours before death, it may be but 31,000 per mm.
In high conditioned animals, with high fever often aggravated by travel, the muscles may be dark and firm, but in those out of condition and in the advanced anæmic stages of the disease the muscles are pale, and there may be subcutaneous œdema below the chest and belly. These last features are especially noted by Smith and Kilborne.
The lungs are usually normal. Sometimes limited congestions, punctiform petechiæ, emphysema and small areas of œdema or hepatization are noticed (Smith and Kilborne).
The pericardium contains a little bloody serum and is marked by petechiæ.
The left heart is usually empty, but the right heart full of fluid, or later, of clotted blood, in the latter case without buffy coat. The endocardium, and especially on the musculi papillares, is marked by petechiæ, punctuate or in considerable patches. The cardiac capillaries are full of blood, with numerous piroplasmata.
The peritoneum often contains a little reddish serosity, and a slight gelatinoid exudation is sometimes found around the kidneys or elsewhere in the abdomen. Petechiæ are frequent.
The stomachs usually show petechiated spots on the mucous membranes, and more or less diffuse congestion. Sloughing of the mucosa at such points is not uncommon, and even perforation of the folds of the third and fourth stomachs. The Bureau of Animal Industry and Lignieres both found these stomach lesions very inconsiderable. The smaller pinhead erosions described by Gamgee were identified by the Bureau of Animal Industry as bites of the strongylus convolutus. The small intestines are usually moderately congested.
The cæcum and colon show more congestion, becoming at times of a deep red or almost black hue, and considerable extravasation of blood may take place. This is especially marked in the rectum, which may be of a port wine hue, comparable to that seen in rinderpest or hæmorrhoidal anthrax. The fæces are often dry and massed in balls in cæcum and rectum, while if diarrhœa has set in, the discharges may be colored with blood or blood elements. Yet in the cases reported by the Bureau serious lesions of the intestines were rather the exception, and some subjects showed scarcely any lesion.
The liver is usually enlarged, averaging three to five pounds heavier than in a healthy ox of the same weight. In these enlarged and congested cases it is of a deep yellowish brown color, and often shows yellow spots on the darker ground. Microscopically each acinus has a bright yellow centre from which yellow radiating canals diverge to join the peripheral gall duct. In the superficial or portal portion of the acinus, the hepatic cells are granular from fatty change, yet the nucleus is usually still recognizable. Toward the central zone it may have disappeared. The further this has advanced, the softer, the more easily pitted and the more friable the liver. The congestion of these radical gall ducts with the dense colored bile, displays the structure of the acini in a clear and beautiful way, which no injection can accomplish. When the affected tissue is teased out and placed under the microscope the inspissated contents of the bile canaliculi may be seen as yellow cylindroid casts sometimes bifurcated to represent the union of the two canals. If stained in Ehrlich’s acid hæmatoxylin, the necrotic elements refuse to take the stain so that the contrast between the dead and the living tissues is enhanced. Fatty degeneration is common in the liver of healthy beef cattle so that this is less significant than the congestion of the acini, and the phenomenal distension of the radical gall ducts with inspissated bile.
The gall bladder is usually full (½ pint to 1 quart or more), and its mucous membrane congested and sometimes petechiated. The bile is thick and viscid, like tar, it may be yellowish green, darkening on exposure and contains hæmatoidin crystals and abundance of flocculi showing bright yellow or orange by transmitted light and reddish brown by reflected light.