54 PROTOPLASM. 



In order to understand the true relation of the so-called 

 intercellular substance of cartilage or tendon to the masses 

 of germinal matter, it is necessary to study the tissue at 

 different ages. At an early period of development, these 

 tissues appear to consist of masses of germinal matter only. 

 As development advances, the formed material increases, 

 and the masses of germinal matter become separated farther 

 and farther from one another. (PI. VI, fig. 16.) The appear- 

 ances of a cell wall around the germinal matter in the 

 fully-formed tissue, and other alterations which occur, and 

 anomalous appearances which often result as age advances, 

 can be even more readily understood upon the view here 

 advanced, than upon the intercellular-substance theory 

 which has been so strongly supported by some observers. 

 See PI. VI, figs. T 6 to 22. 



Of the Formation of the Contractile Tissue of Muscle. 

 A muscle "cell," or elementary part, will consist, like that 

 of cartilage and tendon, of the so-called nucleus, with 

 a portion of the muscular tissue corresponding to it. In 

 general arrangement it closely resembles what is seen in 

 tendon. The contractile material of muscle may be shown 

 to be continuous with the germinal matter, and oftentimes 

 a thin filament of the transversely striated tissue may be 

 detached with the oval mass of germinal matter still con- 

 nected with it, showing that, as in tendon, the germinal 

 matter passes uninterruptedly into the formed material. 

 This contractile tissue is not, like the germinal matter 

 which produced it, in a living state. In the formation 

 of the contractile tissue, the germinal matter seems to 

 move onwards, and at its posterior part gradually under- 



