342 



The Development of the Connective Tissues 



the nucleus onl}^, leaving a space between it and the ground substance. 

 In other words, we have a thickening and transformation of the exo- 

 plasm of the syncytium to form the ground substance of the cartilage, 

 while the nuclei and endoplasm of the syncytium become the cartilage 

 cells. This statement is found to be true in following the development 

 of cartilage from embryo to embryo as well as in the transformation 

 of the connective-tissue syncytium when cartilage grows into it. 



The very early change in the syncytium preceding the formation of 

 cartilage is much more easily followed in tadpoles than in mammals, 

 the pig, for instance. On the other hand, when the cartilage is once 

 formed its further growth is better studied in pig's embryo. • 



Fig. 



Fig. 8. 



Fig. 9. 



Fig. 7. Transition between cartilage and syncytium in a tadpole 9 mm. long. 

 ( X 350 diameters). Hsematoxylin and eosin. 



Fig. 8. Beginning of the occipital cartilage in a pig's embryo 16 mm. long ( x 250 

 diameters). Mallory's stain. 



Fig. 9. Transition between the syncytium and cartilage in an embryo pig 24 mm. 

 long. The specimen had been macerated in Miiller's fluid 24 hours before it was 

 hardened in alcohol ( x 250 diameters). Hsematoxylin and congo red. The central 

 dark zone stained with hematoxylin while the zone of ground substance between it 

 and the syncytium only took the congo red. 



The beginning of the formation of cartilage can be recognized in pig's 

 embryos from 10 to 15 mm. long, in the condensed mass of cells around 

 the chorda. When sections which have been stained in acid fuchsin are 

 studied the connective-tissue syncytium can be followed to the areas 

 of precartilage, but not into them, for the numerous nuclei obscure 

 entirely the exoplasm of the syncytium. In sections stained by Mal- 

 lory's method the beautiful and definite exo^olasm of the syncytium can 

 be followed to the precartilage, and between its numerous nuclei. As 

 this tissue is followed from the region of the spinal cord towards the 

 chorda it is found that exoplasm becomes denser and denser and the 



