CONSTITUTIONAL DISEASES. 109 



It is seen among animals in zoological gardens, and more es- 

 pecially among pregnant animals and those giving milk. The 

 more abundant the lacteal secretion, the more rapid the course. 



It is a disease of adult life, and may be due to a lack of 

 the proper amount of salts in the food. It may be seen during 

 dry seasons, when the ground is dry, there not being sufficient 

 moisture to dissolve the salts. The want of lime salts in the 

 soil; such as swampy, turfy, or sandy soils, poor in phosphoric 

 acid. 



Three theories have been advanced: 



1st. Where the animals do not receive these elements in their 

 food. 



2d. The acid theory, which says that lactic acid is formed 

 in the stomach and dissolves the salts. 



3d. The inflammatory theory — that an inflammation of the 

 periosteum and bone substance takes place. 



The first is probably the best, as the disease can be produced 

 artifically by giving food not containing these salts. 



The action of bacteria has also been suggested. 



What are the symptoms? 



The first symptom noticed is called pica (hunger, depraved 

 appetite) . These animals eat foreign bodies, such as sticks, straw, 

 etc.; they lick the attendant's clothes, or they lick the walls, 

 especially if they have been whitewashed. 



If the disease is allowed to go on, there is trouble in locomo- 

 tion; the animal is stiff, and in walking the legs become more or 

 less entangled by the animal crossing them, and a cracking and 

 snapping of the joints is often heard. Percussion over the bones 

 gives a clear and hollow sound. 



The articulations are hot, swollen, and painful; the animal 

 does not stand still, but is constantly moving. 



These animals seem to prefer lying down, and it is often dif- 

 ficult for them to get up, evincing pain when they do. Efforts 

 at micturition and defecation cause pain. 



At first there is no fever, but later there is often a slight 

 rise in temperature, the pulse becomes increased, and emaciation 

 is well marked. 



The ligaments binding the joints may become loosened from 

 their attachments or may become absorbed, and dislocation or 



