QUARTERLY CHRONICLE OP MICROSCOPICAL SCIENCE. 413 



young animals were examined, and compared with those of 

 adults and with human joints at different ages. These were 

 treated by silver, hgematoxylin, and gold, and studied on 

 surface sections. On examining the head of the femur of a 

 sheep's embryo one and three quarters inch long, the layer of 

 cells described as an epithelium by Todd and Bowman and 

 Reichert was found not to exist ; there is only a homoge- 

 neous substance with nuclei embedded, surrounded by a 

 variable amount of protoplasm. Precisely the same appear- 

 ances are shown by the deeper parts of the cartilage. In 

 more advanced embryos (sheep, two and a half inches long) 

 other places are also found in which the nuclei are rather 

 more separated, brown lines appearing here and there 

 between them. Later on, the brown lines become more 

 frequent and broader, and in some places form a network 

 like that on the surface of serous membranes, but with 

 smaller and more irregular territories. In other embryoes the 

 greater part of the articular surfaces is covered with these 

 flat epithelioid cells. This appearance is due to the gradual 

 development of intercellular substance, which increases, the 

 cells becoming separated by broad bands of matrix, and at 

 the same time becoming irregularly angular, stellate, or 

 elongated, with long processes which dip down obliquely 

 into the matrix. The matrix grows over as well as between 

 the cells, so that in the adult there is a distinct hyaline layer 

 covering the surface of the cartilage. While this is occurring 

 the irregular, stellate, angular, and elongated cells become 

 gradually transformed in parts where the articular surfaces 

 are constantly in contact, with loss of their processes, into 

 the round scattered cells of ordinary cartilage. 



At the time when the articular surface proper has the 

 above epithelioid appearance, the same can be traced over its 

 margin as far as the insertion of the capsule, where, in the 

 adult, vessels and irregularly disposed cells are to be found. 

 The cells are of the same size as those covering the cartilage, 

 but less polygonal, and separated by more intercellular sub- 

 stance, into which they send short knobbed processes, not 

 long and tapering ones, as in the adult. There is every 

 transitional form between these and the cartilage cells, which, 

 as they approach the synovial membrane, begin to exhibit a 

 gradually increasing number of processes, and become more 

 irregular, until they precisely resemble those on the inner 

 layer of the capsule, with which they are connected by freely 

 communicating branches. As development proceeds these 

 appearances are reversed, the cells being widely separated 

 and of irregular forms over the cartilage, whilst near and 



