VEXOUS OBSTEUCTIONS MEGE1MS. 433 



are witnessed, and occasionally there is a tendency, from the 

 shape of the animal's neck, to temporarily check the flow of 

 blood from the head by the collar. A tight-fitting collar 

 may produce this in any animal, but there are horses not 

 easily fitted with an ordinary collar, so as to avoid pressure on 

 the veins of the neck, and in pulling hard these are obstructed 

 and induce symptoms of vertigo. 



Both jugular veins are pressed upon by the collar, and 

 when a horse is driven under such circumstances, it is soon 

 found, especially on a hot day and on hilly ground, that the 

 animal is uneasy. The head is shaken, the ears move con- 

 vulsively, the eyes soon appear bloodshot, and the animal sud- 

 denly rushes forward blindly, and throws itself violently for- 

 wards, often falling on its head, its muscles twitching as if death 

 was imminent. It is not easy to hold a horse in the stage of 

 great excitement, but if the collar is drawn forwards, the flow 

 of blood is restored, and all symptoms disappear with the 

 exception of a feverish excitement for a short time. The 

 pressure by the collar does not absolutely close the veins, so 

 that the heat of the sun has usually to operate in favouring 

 cerebral congestion before megrims is produced. 



I have seen one case in which both jugular veins were 

 closed as the result of phlebitis. The animal, a bay carriage 

 colt, three years old, had only been mouthed, and during a 

 severe illness was bled from both jugulars. He recovered 

 apparently, and so long as he was kept in the stable, and was 

 fed from the rack, no symptoms appeared ; but if turned out 

 to grass, his head began to swell, and if he held his head 

 down long, he rolled over in a fit. I was asked to see this 

 horse, as he was losing flesh in the field, and presenting 

 these strange symptoms, I had no difficulty in finding that 

 both jugular veins were impervious. With obstruction of 



2F 



