PALISADE WOEMS. 401 



break off, and, on being carried . along in .the blood-current, to 

 block up the artery, in which case, the obstruction is called an 

 embolus. Owing to obstructions thus formed, the part usually 

 supplied by the artery becomes more or less paralysed, with the 

 result, in. the case of the intestines, that flatulent colic is produced, 

 on account of fermentation taking place in the delayed food. On 

 the formation of an embolus, there is an immediate attempt at 

 the restoration of the oircidation by side branches of the vessels. 

 We then have a race between the " collateral circulation " and the 

 colic, which will become cured if the function of the part becomes 

 restored before the resulting pain or flatulence has produced fatal 

 consequences, or before twist or invagination (pp. 418 and 419) of 

 the bowel has taken place. These emboli may produce weakness 

 or diminished freedom of action of the hind quarters. 



After the immature worms have undergone another stage of 

 development in their respective aneurisms, they again launch 

 themselves into the blood stream, and by its means they reach the 

 intestine, imder the muqpus membrane of which they again form 

 cysts ; become adult ; and emerge into the intestine, to which they 

 attach themselves and produce eggs. 



As a rule, these aneurisms are not found in foals younger than 

 three months old, and are more frequent in aged horses, than in 

 young ones. 



The dangers due to the presence of palisade worms in the 

 arteries are : embolism, and rupture of the wall of the aneurism, 

 in which case there will usually be fatal bleeding into the 

 abdominal cavity, with rapid failure of the physical powers and 

 bloodlessness of the mucous membranes. 



Although these emboli give rise to no characteristic symptoms, 

 we may suspect their presence when we find that the horse is liable 

 to colic without any errors of diet being to blame, and when the 

 seat of pain appears to be far back, as will be shown by the animal 

 crouching behind and, if obliged to walk, getting his hind legs 

 under him as much as possible. Often, when the animal seems on 

 the point of death, with the surface of his body very oold, he 

 will take a sudden change for the better, owing to the collateral 

 circulation becoming established, and will rapidly mend. In the 

 treatment of this form of worm colic, I would advise a drench of 

 a pint of linseed oil, and 2 oz. of turpentine, followed if necessary, 

 by an ounce of chlorodyne in a pint of water, or half an ounce of 

 the extract of Indian hemp. Besides the symptoms of colic caused 

 by embolism, the presence of the worms in the intestines gives rise 

 to more or less inflammation of the bowels, diarrhoea, generally 

 of a foetid and sometimes bloody character, and slight attacks of 

 colic. The diarrhoea, disturbance of the functions of digestion and 



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