120 FORMATION OF CLUSTERS OF BIOPLASTS. 



tween the former, the cells being embedded in the so- 

 called intercellular substance as bricks are embedded in 

 mortar. ( 111.) No one, however, who has examined 

 cartilage at the different periods of development can 

 accept this doctrine, for he will find that, in its embryo 

 condition, cartilage, like other tissues, consists only of 

 spherical masses of bioplasm, around each of which is 

 the merest trace of soft and delicate formed material. 

 The bioplasm is in direct continuity with the formed 

 material of the matrix, and in some forms of cartilage 

 from the frog the passage of the living formless mat- 

 ter into the formed material can be most positively 

 demonstrated. As the cartilage advances in develop- 

 ment it will be found that the formed material between 

 the masses of bioplasm increases in proportion, so that 

 if several specimens of the same kind of cartilage be 

 taken from the same part of the body of the same 

 species of animal at different ages, and examined, 

 it will be found that the proportion of bioplasm 

 corresponding to a given bulk of cartilaginous 

 tissue gradually diminishes as the tissue advances 

 in age. In specimens of the sternal cartilage of the 

 kitten at birth, of the cat at six weeks and at three 

 months old, and of the full-grown animal which 

 have been prepared, the facts just referred to are 

 clearly demonstrated. The equable increase of the" 

 cartilaginous tissue in all directions is effected, and 

 the expansion of the whole, without folding, crump- 

 ling, contraction, or stretching of any part, is beauti- 

 fully provided for. 



HO. Formation of clusters of bioplasts in carti- 

 lage. In those specimens of cartilage in which each 

 individual mass of bioplasm divides so as to produce 

 clusters of four or more, and these again divide to 

 produce secondary or tertiary clusters, it will be 

 found that the quantity of formed material between 

 the primary clusters is greater than that between the 

 secondary and tertiary clusters, a fact which receives 



