148 
HISTOLOGY OF ANIMALS. 
the non-vascular lamella makes its appearance. In the 
part of the cartilage nearest the articular lamella, as 
seen in a seetion of the articular surface of the bone of 
an Ox , the cells are arranged in columns, but near the 
articular surface their direction is changed. The same 
thing is evident in vertical sections of the articular 
cartilage of the humerus of a Pig , in which also, a well- 
developed non-vascular lamella is visible, and as in the 
Ox the cartilage-cells near the articular surface are 
arranged at right angles to those nearest the bone. In 
a vertical section of the head of a femur of a female, 
aged nineteen, the same arrangement is perceptible ; 
but it will be noticed, that the articular lamella is 
sparingly developed. In a vertical section of the 
corresponding bone of a female upwards of seventy 
years of age, in which the arrangement of the cells 
in the cartilage precisely resembles that in the preceding 
case, the non-vascular lamella is nearly twice as broad. 
If the free surface of the articular cartilage of the young 
woman be examined, the cells will be seen to be more 
or less flattened, and to contain nuclei ; in the older 
woman the cells are present, but the nuclei have dis- 
appeared. Having demonstrated the principal varieties 
of articular cartilage, it now becomes necessary that I 
should speak of the synovial membrane, which is said 
by some persons to invest the whole articular surface. 
In the foetal condition of man and of the higher mam- 
malia each joint is covered with synovial membrane and 
an epithelium ; as soon, however, as the joint is used, the 
