206 DISEASES OF METABOLISM 



Diabetes Mellitus. — Definition. — ^Diabetes mellitus is a dis- 

 ease marked by the passage of an excessive amount of urine 

 containing an excess of grape sugar. 



Occurrence. — Except in dogs, where it is not common, the 

 disease is extremely rare in animals. 



Etiology. — The causes are not well understood. Heredity, 

 direct injury, severe mental shock, nervous strain and worry 

 are accused in man. 



Symptoms. — ^The principal symptom is a copious secre- 

 tion of urine with increased thirst. The patients are languid, 

 grow thin but retain a splendid appetite. A chemical analysis 

 of the urine will show it to contain 4-8 per cent, grape sugar. 

 In the advanced stages cataract (c. diabetica) and ulceration 

 of the cornea have been observed. 



Course. — The course of the disease is chronic lasting for 

 months but ending fatally. Death may occur suddenly under 

 coma probably due to an intoxication with /3-oxybutyric acid 

 which accumulates in the tissues and blood in large quanti- 

 ties and is eliminated in the urine. 



Treatment. — The treatment of diabetes mellitus is largely 

 dietary and symptomatic. 



GOUT. PODAGRA. 



Definition. — Gout is a painful constitutional or diathetic 

 disease with arthritis and an increase of uric acid in the blood. 

 There is a gradual deposition of chalky material (sodium 

 biurate) in and about the joints. The disorder may be acute 

 or chronic. In animals gout occurs only in birds. 



OBESITY. 



Definition. — Obesity or corpulence is an excessive develop- 

 ment of bodily fat occurring principally in the subcutis. It 

 may be hereditary. In animals it is usually due to high 

 feeding and lack of exercise. For edible animals a certain 

 corpulence is desirable. It is also of value in horses as it 

 enhances their appearance and makes them more salable. 



Obesity is one of the causes of sterility in the female and 



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