254 HORSE, SWINE AND POULTRY DISEASES 



if an etiologist is bound to possess universal knowledge within the 

 scope of his special studies, to be his opprobrium and his puzzle. 



Treatment. When there is a known or suspected cause the 

 treatment should be directed toward this factor. If due to local in- 

 flammation of the hock or foot, only this local lesion should be 

 treated. If it remains after the local lesion has healed, or if we have 

 no assignable cause, the best results have followed the sectioning 

 of the lateral extensor of the foot. A competent veterinarian alone 

 should undertake this operation. 



THROMBOSIS. 



There are certain forms of lameness which are very peculiar in 

 their manifestation, and which to the nonprofessional mind must 

 appear to belong to the domain of mystery or theory instead of occu- 

 pying a well-established position among the subjects of equine 

 pathology. Yet they are no less susceptible of actual demonstration 

 and of positive comprehension than many facts which, plain and 

 familiar to the general understanding now, were once ranked among 

 things occult and unsearchable. A thrombus, considered as a cause 

 of lameness, may find a place among these understood mysteries. 



Cause. Under certain peculiar conditions of inflammation of 

 the blood vessels, and also in aneurisms, clots of blood are sometimes 

 formed in the arteries and find their way in the general circulation. 

 At first, while very small, or sufficiently so to pass from one vessel 

 to another, they move from a small vessel to a larger, and from that 

 to one still larger, constantly increasing in size until at some given 

 point, from their inability to enter smaller vessels, their movement is 

 finally arrested. The artery is thus effectually dammed, and the 

 clot in a short time cuts off completely the supply of blood from the 

 parts beyond. This is thrombosis, and it often gives rise to sudden 

 and excessive lameness of a very painful character. 



Symptoms. Thrombi may form in any of the arteries of the 

 body, and doubtless have been the cause of many cases of lameness 

 which could never be accounted for. If they exist in small arteries 

 their diagnosis will probably fail to be made out with certainty, but 

 when situated in the larger trunks a strong suspicion of their pres- 

 ence may be excited. In some cases they may even be recognized 

 with positive accuracy, as when the vessels which supply the posterior 

 extremities are affected by the Blocking up of the posterior aorta or 

 its ramifications. 



The existence of thrombosis of the arteries of the hind leg may 

 always be suspected when the following history is known : The gen- 

 eral health of the animal is good, but symptoms of lameness in one 

 of the legs have been developed, becoming more marked as^ he is 

 worked, and especially when driven at a fast gait. But the disturb- 

 ance is not permanent, and the lameness disappears almost imme- 

 diately upon his being permitted to rest. There is an increase of 

 the difficulty, however, and, though he may walk normally, he will, 

 when made to trot, very soon begin to slacken his pace and to show 

 signs of the trouble, and if urged to increase his speed will become 

 lamer and lamer; an abundant perspiration will break out; he will 



