69 



the nerve centers and muscles. A peculiar anatomical feature of the 

 horse's liver doubtless contributes to this, namely, the persistence, 

 throughout life, of several considerable veins leading directly from the 

 veins of the stomach and intestines (portal veins) into the posterior 

 vena cava and heart. 



This condition, common to foetal mammals, persists through life in 

 the solipeds only, among our domestic animals. In all others the 

 portal vein has no communication with the vena cava except through 

 the capillaries of the liver. With the direct channel the rich, crude 

 blood coming from the intestines is drawn at once into the general cir- 

 culation unchanged bj' the secretion in the liver and the chemical 

 changes therein effected. Hence this disease is peculiar to solipeds. 

 It has been noticed rather more frequently in mares than horses, 

 attributable, perhaps, to the nervous excitement attendant on heat, 

 and to the fact that the unmutilated mare is naturally more excitable 

 than the docile gelding. 



Syviptoms. — ^In the milder forms this affection may appear as a lame- 

 ness in one limb, from indefinite cause, succeeding to some sudden 

 exertion and attended by a dusky-brown color of the membranes of the 

 eye and nose and some wincing when the last ribs are struck. The 

 severe forms come on after one or two days of rest on a full ration, when 

 the animal has been taken out and driven one hundred jjaces or more. 

 The fire and life with which he had left the stable suddenly give place 

 to dullness and oppression, as shown in hea^ang flanks, dilated nostrils, 

 pinched face, perspiring skin, and trembling body. The muscles of the 

 loins or haunch become swelled and rigid, the subject moves stififl}' or 

 unsteadily, crouches behind, the limbs being carried semi-flexed, and he 

 soon drops, unable to support himself. A\Tien down, the body and limbs 

 are moved convulsively, but there is no power of co-ordination of move- 

 ment in the muscles. The pulse and breathing are accelerated, the 

 eyes red with a tinge of brown, and the urine, if passed, is seen to be 

 highly colored, dark bi'own, red, or black, but it contains neither blood 

 clots nor globules. The color is mainly due to haemoglobin and other 

 imperfectly elaborated constituents of the blood. 



It may end fatally in a few hours or days, or a recovery may ensue, 

 which is usually more sj^eedy and perfect if it has set in at an early 

 stage. In the late and tardy recoveries a partial paralysis of the hind 

 limbs may last for months. A frequent sequel of these tardy cases is 

 an extensive wasting of the muscles leading up from the front of the 

 stifle (those supplied by the crural nerve), and a complete inability to 

 stand. 



The prevention of this serious affection lies in restricting the diet and 

 giving daily exercise when the animal is not at work. A horse that 

 has had one attack should never be left idle for a single day in the stall 

 or barn -yard. When a horse has been condemned to absolute repose 

 on good feeding he may have a laxative (one-half to 1 pound Glauber 



