Gamgee records a carcinoma of the pancreas of a mare.
Carcinoma is more frequent in this organ in dogs, the neoplasm having an irregular form, an imperfect line of delimitation from surrounding parts and a hard, fibrous stroma enclosing caseous centers, undergoing fatty degeneration.
Nocard reports an epithelial tumor of the head of the pancreas in a bitch. The animal which had been ill for six weeks was debilitated, emaciated, and icteric with a marked abdominal swelling. It died two weeks later, and necropsy revealed a whitish sublumbar tumor, the size of a large apple, with irregular rounded projections. This pressed on the posterior vena cava, surrounded the vena portæ and gall duct and completely closed the latter. Microscopic examination showed it to be an epithelioma. The liver was undergoing cirrhosis.
Treatment, usually hopeless, would be by laparotomy. If actinomycosis were present give potassium iodide.
DISEASES OF THE SPLEEN.
No guidance through palpation or secretion. Leukæmia. Lymphadenoma. Spleen a favorite culture ground for microbes. Congestions, engorgements, ruptures. Safety valve to portal system and liver. Rhythmic splenic contractions under reflex action.
The spleen even more than the pancreas is so deeply seated and so surrounded by other organs, that its diseases are not readily appreciable by physical examination, while the absence of any special secretion excludes the possibility of diagnostic deductions through this channel. Even the relation of the condition of the organ to the number of the leucocytes and red globules fails to afford trustworthy indications of disease, since leucocytes originate in other tissues as well as the spleen, and the destruction of red globules may take place elsewhere. Yet an excess of eosinophile leucocytes in the blood suggests hypertrophy or disease of the spleen, and an excess of leucocytes in general is somewhat less suggestive of disease of this organ (see Leucocythemia). If adenoma is further shown, in enlargement of lymphatic glands elsewhere there is the stronger reason to infer disease of the spleen.
The physiological relation of the spleen to the blood especially predisposes it to diseases in which the blood is involved. The termination of splenic capillaries, in the pulp cavities, so that the blood is poured into these spaces and delayed there, opens the way, not only for the increase of the leucocytes, and the disintegration of red globules, but for the multiplication of microörganisms which may be present in the blood, and for a poisoning (local and general) with their toxins. Hence we explain the congestions, sanguineous engorgements and ruptures of the spleen in certain microbian diseases (anthrax, Southern cattle fever, septicæmia, etc.)
We should further bear in mind that the spleen is in a sense a safety valve for the blood of the portal vein, when supplied in excess during digestion. In this way it protects the liver against sudden and dangerous engorgements, but it is itself subjected to extreme alternations of vascular plenitude and relative deficiency. This may be held to take place largely under the influence of the varying force of the blood pressure in the portal vein, but according to the observations of Roy on dogs and cats, it is also powerfully influenced by muscular and nervous action. He found rhythmic contractions of the organ due to the muscles contained in the capsule and trabeculæ, repeating themselves sixty times per hour, and which might be compared to tardy pulsations. He further found that electric stimulation of the central end of a cut sensory nerve, of the medulla oblongata, or of the peripheral ends of both splanchnics and both vagi caused a rapid contraction of the spleen. The spleen may thus be looked on not only as a temporary store-house for the rich and abundant blood of the portal system of veins during active digestion, but also as a pulsating organ acting under the control of nerve centres in the medulla. That the various ascertained normal functions of this viscus may be vicariously performed by others, as shown in animals from which it has been completely extirpated, does not contradict the occurrence of actual disease in the organ, nor the baleful influence of certain of its diseases on the system at large.