82 



HISTOLOGY 



matrix which stains with haematoxylin. The cells are not flattened as in 

 connective tissue. They are lodged in well-rounded lacunae (Fig. 69), 

 bounded by capsules and zones of blue-staining matrix; and they are fre- 

 quently arranged in pairs or small groups such as occur in other forms 

 of cartilage. Their protoplasm is extensively vacuolated and is some- 

 times shrunken. 



"Vesicular supporting tissue" is a form of precartilage which consists 

 of large vesicular cells in close contact, bound together by firm walls; it 

 is a "cartilage without a matrix." In many invertebrates it is an impor- 

 tant tissue, but in adult mammals it is of limited occurrence. In man 

 such a tissue is said to be present on the inner surface of the tendon of 

 insertion of the M. quadriceps femoris, and in the sesamoid cartilage in 

 the tendon of the M. peronaeus longus. This form of cartilage resembles 

 the notochordal tissue at a certain stage of development, and it is called 

 "chordoid tissue" by Schaffer. 



NOTOCHORDAL TISSUE. 



Although the notochord is of entodermal origin (cf. p. 38), it gives 

 rise to a tissue which has often been called cartilage. Notochordal tissue 



* f 



FIG. 70. A PORTION OF A NUCLEUS PULPOSUS FROM A HUMAN EMBRYO OF THE SIXTH MONTH. X 225. 



The notochordal syncytium is seen in the center of a mucoid matrix. The vertebrae are toward the right 



and left, beyond the limits of the figure. 



differs, however, from any of the types thus far considered. The principal 

 stages in its development in the pig have been described by Williams 

 (Amer. Journ. Anat., 1908, vol. 8, pp. 251-284), whose account may be 

 summarized as follows: 



