Abstract O’NEIL (1943) described the anatomy and architecture of the keel cyst or keel bursa of the domestic fowl to differ considerably from a blister in its anatomical detail. Although O’Neil suggested the term “bursa synovialis presternalis” to be more precise, the terms “breast blister,” “keel cyst” and “keel bursa” are currently utilized to depict the situation encountered with turkeys and chickens. Lucas and Stettenheim (1968) suggest the term sternal bursa (Bursa sternalis). The cause of keel bursa enlargement has been attributed to a wide array of factors. Type, particle size, depth, frequency of addition and dampness of litter have been evaluated by Smith (1956), Bezanson and Stephenson (1958), May and Noles (1966), Stephenson et al. (1960) and Adams et al. (1967). In addition to litter, other types of floor and brooder coverings have been investigated by Koonz et al. (1963) and Adams et al. (1967). Influences of equipment on bursa . . .