Slight hæmorrhages may appear in any of these structures. Lymphoid growths may appear in a number of other organs as the liver, heart, lungs, kidneys, bowels, tonsils, the different blood glands, the serosæ and the retina.
Genera affected. It has been seen mainly in dogs, but also in horse, ox, pig, cat and mouse. Nocard has collected the following cases: horse 9, cattle 6, pig 5, dog 22, cat 1.
Leisering found a horse’s spleen weighing 28 kilogrammes. Johne found a pig’s spleen of 2.4 kilogrammes.
Causes. The primary causes of leukæmia are unknown. As in anæmia all unhygienic conditions are invoked as causes. That it is not due to simple hypertrophy or irritation of the leukogenic centers is plain, as it does not follow on ordinary diseases and injuries of these parts, but what is the precise nature of the morbid cause has so far eluded us.
Symptoms. Pallor of the visible mucous membranes, listlessness, lack of energy and endurance, breathlessness and perspiration on the slightest exertion, ardent thirst, rapidly advancing emaciation, unsteady gait, stiffness or lameness, lies most of the time, walks with pendent head, and jaws open, small, weak pulse, anæmic murmur in the heart, enlarged lymph glands, or spleen felt beneath the left lumbar transverse processes in the ox, or in the left hypochondrium in the horse. Bleeding from the nose or elsewhere, slight hæmorrhage into the conjunctiva, irritable conditions of the bowels, diarrhœa and dropsies are suggestive. The blood when obtained in epistaxis or drawn by a needle prick may be pale rose, brownish or grayish brown instead of red, and under the microscope shows the enormous excess of leucocytes—the ratio to the red being sometimes 1: 2, or even more, in the human subject. In the domestic animals the following ratios have been made by actual count: 1: 85 (Leblanc and Nocard), 1: 50, 1: 45 (Mauri), 1: 20 (Nocard), 1: 15 (Siedamgrotzky), 1: 12 (Forestier and Laforque). The normal average for the domestic animal according to Nocard is 1: 900. This great relative excess of white globules serves to distinguish this malady from anæmia, and its persistency is a means of diagnosis from transient leucocytosis.
The red globules are always reduced in number in the horse and dog to 5,082,000, and even 2,050,000 per cubic millimetre, while the normal is 7,500,000 (Nocard).
In clotting, the blood forms an extensive buffy coat, and in solipedes which normally show this, the blood set in a test tube forms three strata, the upper slightly yellow, semi-transparent and formed of fibrine; a median of a dull, opaque white color and formed mainly of leucocytes and blood plates, and a lower of a violet red and formed mainly of red globules.
The amount of fibrine is variable. It becomes granular when beaten. Albumen is variable but usually reduced.
The visible mucous membranes are bloodless and of a clear porcelain white. The walk becomes weaker, fore feet wide apart and the hind limbs partly flexed, head and neck extended, and breathing labored. The breathing may be with constant stertor, the bowels torpid and tympanitic, or loose and fœtid, dropsies and hæmorrhages ensue, and the patient dies in complete marasmus.
Duration. The disease may prove fatal in less than a month, or it may last for three, six, or eight months. It is mostly fatal.