The symptoms follow almost the same course as in the horse, and one may distinguish three periods:—
I. Period of onset. The symptoms which mark the onset of the disease are moderate fever, which progressively increases, and acceleration of respiration and of circulation. The number of the respiratory movements rises to twenty or twenty-five per minute, those of the pulse to fifty, sixty, or eighty. The conjunctiva becomes injected, and then of a yellow tint. At this period the appetite never disappears completely, rumination is regular, and there is neither tympanites nor colic.
These general symptoms, which are not of special significance, are supplemented by more precise local symptoms—an abortive, difficult and painful, cough which is easily induced, and a whitish discharge. The rusty expectoration which is characteristic of simple pneumonia in the horse and in man has never been observed.
Percussion discloses partial dulness, usually on one side, in the lower region of the chest: the respiratory murmur in this region is ascertained by auscultation to have diminished, whilst in the upper part and also on the opposite side the respiratory murmur is increased.
II. Period of exacerbation. This period is characterised by accentuation of all the symptoms: the temperature rises, and may attain 104° Fahr.; the submaxillary artery is tense; the dulness becomes more marked, whilst crepitant and mucous râles are heard. In the portions still unattacked the function of the lung is exaggerated in order to make up for the defect of the diseased parts, and the respiration becomes juvenile.
The appetite, which previously had been maintained, diminishes considerably, without, however, entirely disappearing, and intense thirst sets in, as a consequence of the fever.
III. Period of crisis. The general symptoms remain stationary for four or five days; the respiration, which is always affected, sometimes becomes as rapid as thirty to forty per minute; the tubal souffle which invariably occurs in pneumonia of the horse is not always clearly audible.
Terminations. (1.) Resolution.—This is indicated by the attenuation of all the symptoms and the disappearance of fever, which gradually sinks from 105° to 101° Fahr. The respiratory movements become fuller and fewer in number, the pulse slower, and the artery softer and more compressible. The cough changes its character, is stronger, more sonorous and prolonged, and is accompanied by the free discharge of muco-pus. The dulness descends, and the tubal souffle, if previously existing, is replaced by the returning crepitant râle. In general the disease runs its course in eight to ten days in young and in fourteen to fifteen days in aged subjects.
(2.) Death by asphyxia is almost the only fatal termination of pneumonia in the ox. It occurs in one-third to one-fourth of the subjects attacked. Its approach is announced by a deep mahogany-red coloration of the conjunctiva. The pulse becomes very rapid, 100 to 110 per minute, thready, small, and almost imperceptible, whilst the beating of the heart is strong and tumultuous. Respiration is rapid and very laboured (50 to 70 per minute). The animal’s attitude is typical; it stands with its limbs thrust out, its head extended, its nostrils dilated, and its mouth half open, discharging foamy and viscous saliva. Throughout the greater portion of the lung gurgling sounds and crepitant mucous râles can then be detected.
(3.) Cases ending in gangrene and suppuration are excessively rare, and others resulting in chronic pneumonia have not been authoritatively described.