THE BONES AND JOINTS. 749 



Carcinoma. Primary carcinoma is of doubtful occurrence in the 

 bones. Most of the structures thus named have doubtless been sar- 

 comata or eudotheliomata. Secondary carcinoma, on the other hand, 

 as a result of metastases or local extension, is not infrequent. Metas- 

 tatic carcinomata may occur in the bones of various parts of the body 

 at the same time, and are most apt to be secondary to carcinoma of the 

 mamma. 



Cysts. These most frequently occur in the maxillary bones (page 349) 

 in connection with the teeth. They may be unilocular or multilocular, 

 and contain clear serum or a mucous or brown fluid, and sometimes cho- 

 lesteriu. They may be lined with epithelium. They begin in the interior 

 of the bone, and, as they increase in size, expand it until they may be 

 covered with only a thin shell of bone. They may reach a large size, 

 even as large as a child's head. 



Dermoid Cysts are occasionally found in connection with the bones, 

 particularly of the skull. ' 



The Joints. 



For a description of the dislocations, misplacements, and injuries of 

 the joints we refer to works on surgery. 



DEGENERATION. 



Fatty degeneration of the cartilage cells, mucous degeneration, and 

 fibrillation of the strorna with softening, and often roughening, of the 

 joint surfaces, calcification and amyloid degeneration, may occur in 

 inflammation, or as a senile alteration, or under other conditions. The 

 cartilage is usually, under these conditions, whiter and more opaque than 

 normal. 



INFLAMMATION. (Arthritis.) 



Exudative Arthritis. The earlier stages of acute inflammation of the 

 synovial membranes are better known from experiments on animals than 

 from post-mortem examinations. The first changes are swelling and 

 congestion of the membrane, with increased growth and desqtfamation of 

 the lining cells, and infiltration of the membrane with lymphoid cells. 

 These conditions are soon followed by an exudation. 



In Serous Arthritis the accumulation of serum within the synovial sac 

 is the most prominent lesion. The disease may terminate in recovery, or 

 become chronic, or pass into the suppurative form. It may be incited 

 by contusions, penetrating wounds, gonorrhoea, rheumatism, or it may 

 occur without evident cause. 



Sero-fibrinous Arthritis may occur under the same conditions as those 

 which lead to simple serous inflammation. The fibrin may be present 



1 For a resume and bibliography of the pathology of bone see Schmidt in Lubarsch 

 and Ostertag's " Ergebnisse, " Jahrg. iv. for 1897, p. 531 ; also Jahrg. v. for 1898, p. 895. 



