198 CONNECTIVE TISSUE. 



these are transformed into regular bone. The older a person 

 grows, the less hyaline cartilage is found in his body. 



Kolliker made the curious discovery of a " parenehymatous or cellular" 

 cartilage, constructed wholly of cells, without any trace of basis-substance. 

 Among others, the chorda dorsalis, a light line close above the earliest forma- 

 tion of the central nervous system in the embryo, is considered to be such a 

 parenehymatous cartilage. Such a thing, however, is contrary to all we know of 

 what could possibly be any variety of connective tissue. According to V. v. 

 Mihalkovics, the chorda dorsalis is no cartilage at all, but a duplicature of the 

 outer, epithelial germ-layer (Toldt). If this be correct, it would be another 

 instance of an epithelial elongation which, after returning to the condition 

 of an embryonal and medullary tissue, gave rise to connective-tissue forma- 

 tions. We know that this is the case with the thyroid body and the enamel- 

 tissue of the teeth. 



THE STRUCTURE OP HYALINE CARTILAGE.* 



Fresh, articular cartilage is a suitable object for the study of 

 the histology of hyaline cartilage. If we place a thin section, to 

 which is added a drop of one-half per cent, solution of common 

 table-salt, under the microscope, with an immersion lens No. 10, 

 we will find a number of details heretofore overlooked. The 

 following description is a study of a specimen taken from a hori- 

 zontal section of the condyle of femur of a young, full-grown dog ; 

 it answers to the corresponding cartilages of the cat and the 

 rabbit. 



The bodies of the cells appear finely granular, bounded by a 

 somewhat denser layer. The contour of the cartilage cell being 

 accurately in focus, there appears between the cell and the basis- 

 substance a light, very narrow rim, which is traversed by numer- 

 ous extremely delicate, radiating, grayish thorns or streaks. All 

 these thorns are conical, the broad base emanating from the body 

 of the cell and the thin point directed toward the basis-substance. 

 Wherever two cells lie close together, the light rim between them 

 is pierced in a transverse direction by grayish threads. 



When in the cell the nucleus is distinctly visible, its shape 

 will be found to correspond to the shape of the cell- body, and in 

 its finely granular interior the bright nucleolus will be usually 

 apparent. A narrow light rim is found to surround the nucleus, 

 which, on being sharply focused, shows radiating thorns, whose 



* Translated from "Studien am Knochen und Knorpel." Wiener Mediz. 

 Jahrbiicher, 1872. 



