CONSTITUTIONAL DISEASES. 113 



There are certain districts or regions of this country, as Long 

 Island, New Jersey, Ohio, and Illinois, where this disease is quite 

 common. It does not seem to affect the Yankee horses, as a rule. 



The climate and the soil have something to do with it; there 

 is absence of some of the salts. There may be an absence of some- 

 thing in the soil or in the feed which has to do with the formation 

 of bone. 



It is possible that this disease may be of germ origin, as in 

 some respects it resembles diseases of this sort. 



What is the morbid anatomy? 



The vascular and fibrous tissues become increased without 

 any increase of bone. 



The contents of the cells and the cavities become abnormally 

 developed, the bones thickened, especially those of the lower jaw. 

 The bones of the extremities and the articulations are often en- 

 larged. In some cases ulceration of the cartilage may be present. 



The bones of the animal are brittle and very prone to fracture; 

 if the animal were pulling a big truck and should fall, there is a 

 liability to fracture, especially of the ilium; it is often necessary 

 to differentiate this condition from other troubles. 



Give the symptoms; 



These are somewhat characteristic. 



We usually get a history — that the animal is a poor feeder; at 

 first they were good feeders, were in good condition, but they began 

 to fall away and did not eat well. They have a peculiar tucked-up 

 appearance of the abdomen. 



If you make them trot, they travel with the so-called short 

 dog-trot gait; there is no knee action, the front legs are stiff and 

 straight, and they often look as though they were going fast, but 

 they are not. 



The transverse diameter of the lower jaw is increased; ordi- 

 narily it may be, say, half an inch or so, while in this disease 

 it may be three or four inches. Pressure on the diseased bones 

 causes pain. 



Very often, in young animals, the roots of the molar teeth 

 give prominence to the face, and we should be careful not to mis- 

 take the two. In Shetland ponies it is often difficult to diagnose, 

 as the bones of the face are naturally prominent. 



