ABSCESS IN BONES. 177 



tlie bone, and found its way to the surface of the skin. 

 In long-continued cases of lameness, with enlargement of a 

 bone, as in the specimen, the practitioner should open the 

 enlarged portion by the trephine, the probabilities being that 

 he will find either pus, or a sequestrum, or both, imprisoned, 

 and that their removal will bring on a favourable termina- 

 tion. In the case from which the specimen was obtained, no 

 other reason could be given for the abscess than that the pole 

 of the carriage, by continually striking this part, brought on 

 inflammation and suppuration of the medullary membrane, as 

 well as periostitis. 



When the trephine has to be used, it is nearly always neces- 

 sary to cast the patient ; making a careful incision on to the 

 diseased bone ; avoiding injury to important blood-vessels and 

 nerves ; dividing the muscular structures in the direction of 

 their long axes ; separating all the soft tissues from the bone 

 before the trephine is applied, or its teeth will become clogged ; 

 and, finally, washing out the abscess thorouglily with water in 

 which a small quantity of the pure carbolic acid has been dis- 

 solved ; and leaving the lower portion of the wound in the soft 

 structures open, to allow the escape of the discharges. 



Mr. Stanley says that "circumscribed abscess is, in some 

 cases, attributable to the softening of tubercular matter, analo- 

 gous to a pulmonary vomica, and that the contents may be 

 discharged, leaving a cavity resembling a tuberculous cavity in 

 the lungs." The circumscribed abscess, according to the same 

 writer, " usually remains of a small size, but in some cases it 

 has enlarged much beyond the natural limits of the bone. 

 Such an enlargement is not the effect of a simple expansion 

 of the walls of the bone ; for in some of these cases the osseous 

 walls of the abscess have increased in tliickness, with enlarge- 

 ment of the cavity. The process consists of the combined 

 action of absorption on the inside of the abscess, and of osseous 

 deposit on its outside, whereby its osseous walls may acquire 

 any degree of thickness, according to the predominance ot 

 absorption in the one direction, or of deposit in the other." 



