388 



CHAPTER XVI. 



Serous Cysts. 



GENERAL KEMARKS — CAPrED HOCK — CAPrED ELBOW — SEROUS CYST NEAR 



THE WITHERS. 



General Remarks. 



A SEROUS cyst is a cavity formed by an effusion of serous fluid into con- 

 nective tissue, the fibres of which, by the consequent pressure, " are squeezed 

 together and thus form the membranous wall of the cyst, wliich subsequently 

 becomes thickened by new growth of fibrous tissue" {Erichsen). A cyst of 

 this kind may be defined " as a cavity resulting from the abnormal distension 

 of a natural space, surrounded by a more or less distinct wall, and filled with 

 fluid or semi-solid matter " (Erichsen). These enlargements are specially 

 liable to occur as a result of inflammation, immediately underneath those por- 

 tions of the skin which cover bony prominences ; becau&e, in these positions, 

 the extent of the seat of injury being narrowly limited between the bone 

 and the skin, a closely confined effusion is more likely to take place, than in 

 a part surrounded by soft structures. 



Serous fluid (p. 13), which is the watery fluid we find on opening 

 a blister, often accumulates at the point of the hock, or at the 

 back of the elbow, causing these parts to become " capped," as a 

 result of injury. Unlike synovia, serous fluid generally becomes 

 quickly organised into fibrous tissue. 



These enlargements, though unsightly, rarely cause uneasiness 

 to the horse. They may be treated boldly by surgical means, as 

 they are well removed from any important structures. Tf the 

 case be of long standing and the seat of injury be on the surface 

 of the body, the distended condition of the skin which covers the 

 part, will persist after the subsidence or removal of the 

 enlargement. 



Capped Hock. 



Ordinary capped hock is a serous cyst situated at the point of 

 the hock (Fig. 137), between the cap of the perforatus tendon and 

 the skin (Fig. 28). It is usually the result of blows, wdiich are 



