262 A MANUAL OF VETERINARY PHYSIOLOGY 



The pancreas in structure resembles the salivary glands, in 

 being compound tubular, but in it may be seen with the naked 

 eye spherical or oval bodies, which are obviously not ordinary 

 pancreatic tissue ; these are known as the Islands of Langerhans. 

 The islands are composed of a group of cells surrounded by a rich 

 capillary network of bloodvessels, and the view has been advanced 

 that they are the seat of the production of the internal secretion. 

 Ligature of the pancreatic duct causes the ordinary gland tissue 

 to atrophy, but does not affect the islands, nor does ligature 

 produce glycosuria. This is evidence in favour of their furnish- 

 ing the internal secretion, but there are other observers who 

 consider the islands are connected with the ordinary pancreatic 

 secretion. 



Diabetes. — In the forms of glycosuria hitherto dealt with, its 

 production has been experimental. But there is a pathological 

 condition in which much the same symptoms are present, and 

 though, so far as we know, the herbivora do not surfer from this 

 disease, it has been described in the dog, and under any circum- 

 stances its features in man are of interest to us. In diabetes the 

 sugar in the blood, instead of being o-i per cent., as it normally 

 is in man, may rise to 0-4, or even as high as 07 or 1 per cent. 

 In consequence of the tissues being unable to consume the dextrose 

 brought to them, the sugar passes off by the urine, and the body 

 is starved of its source of heat and energy. As the disease ad- 

 vances, not only sugar, but products of deranged protein and 

 fat metabolism, appear in the urine, such as acetone, aceto-acetic 

 acid, and oxybutyric acids. These acids, by combining with the 

 alkali of the blood, reduce the carbon dioxide carrying capacity 

 of the fluid, and, in consequence, the carbon dioxide accumulates 

 in the tissues, and diabetic coma results. 



Pathological. 



The most common pathological condition of the liver is Jaundice, 

 and the majority, if not all, cases of jaundice are obstructive — viz., 

 there is some obstruction to the free pouring out of bile ; in con- 

 sequence there is a backward pressure, which being greater than the 

 low blood-pressure under which bile is secreted, the bile is reabsorbed, 

 and stains the tissues yellow. There is also a form of jaundice 

 affecting the horse and dog in South Africa, due to a parasite in the 

 blood ; in these cases the yellow tint is derived from the destruction of 

 red corpuscles stimulating the production of bile (see p. 243) . Biliary 

 Calculi, consisting largely of cholesterin, are not uncommon in rumi- 

 nants, but rare in the horse. Fatty Liver is common in all animals 

 overfed and underworked. In the horse it may lead to Rupture 

 of the liver during work. Enlargements of the liver are very 

 common as the result of vascular disturbance elsewhere ; it is not 

 uncommon as a sequel to pneumonia, strangles, and other pro- 

 longed febrile changes. Abscess of the liver is rare, but not un- 



