20 8 DISEASES OF THE DOMESTIC ANIMALS 



True diabetes insipidus, as seen in the human and occasionally in 

 horses, is a specific chronic disease and not a mere symptom of 

 other disorders. The exact nature of diabetes insipidus is un- 

 known, but it is thought to be a vasomotor disturbance with dilata- 

 tion of the renal vessels caused by reflex or direct irritation of the 

 medullary centre, of the abdominal sympathetic ganglia, or local 

 irritation of the kidneys. In the horse, the symptoms consist in the 

 passage of a large amount of pale, acid urine (7 to 13 gallons 

 daily), of low specific gravity (1001 to 1015), associated with 

 colicky pains, great thirst, anorexia and weakness. This condition is 

 more strictly a temporary diuresis or polyuria, but, if untreated, 

 may result in a chronic condition or true diabetes insipidus, with 

 much emaciation, exhaustion and even death. In the human, the 

 disease may continue for a long period of years without any serious 

 result. 



Polyuria in horses is seen as a symptom in strangles, influenza, 

 pleuro-pneumonia, glanders, leukemia, and disease of the brain. In 

 the true or idiopathic diabetes insipidus of man there are no con- 

 stant lesions to be found after death. Such cases rarely occur in 

 horses. In the human, exposure to cold, fright, overexertion, inani- 

 tion, functional nervous disorders, traumatism to the head, sun- 

 stroke, ingestion of large amounts of fluid, and convalesence from 

 acute disease, are supposed to have some causal relation. Also 

 brain disease (tumor, inflammation), or abdominal disorder (as 

 peritonitis, tumor, aneurism) may produce polyuria, but this is not 

 diabetes insipidus, but diuresis dependent upon irritation of the 

 brain or kidney. 



Treatment. — In the ordinary form in the horse, following the 

 use of musty or moldy oats, a change of diet is the chief indication. 

 Where sound food is not procurable, kiln-drying, steaming or 

 boiling the moldy grain will kill the fungi and lessen the injury 

 caused by the improper diet. This injury may consist in the in- 

 fluence of a toxin upon the central or local renal vasomotor system. 



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