i8 



FIRST LECTURE. 



nective tissue has also formed those elastic fibres, which we 

 have just met with in cartilage. 



From whence, however, does the tissue cement and the 

 intercellular substance come ? Have they been inserted from 

 the neighborhood between the cells, or have the cells them- 

 selves produced these substances ? 



The latter is the case. These substances were once con- 

 stituents of the cell body, at one time represented protoplasm. 

 The formation of these substances was sometimes compared 

 more to a secretive act of the cell, at others, more to a meta- 

 morphosis of the outer portion of the cell body. We think 

 both occur, and the difference between these views is, in fact, 

 of little importance. 



A deposition may also take place from without upon a 

 single cell or a cell-complex and enter into a closer union 

 with it. The mammalial ovum (Fig. 5), shows a capsule. 

 It is the elaboration of the small cells (a) covering the ovu- 

 lum. 



The capsule of the cartilage cells appears very similar to 

 the ovum capsule. Its origin, however, is entirely different. 



The cartilage cells have 

 themselves formed the car- 

 tilage capsule. We shall 

 return to this subject later. 

 The glands (Fig. 26), con- 

 sist of secretory cell-com- 

 plexes surrounded by a 

 hyaloid covering, the so- 

 called membrana propria. 

 This is not a secretory pro- 

 duct of the cell-aggrega- 

 tion, as was formerly assum- 

 ed. The membrane is trans- 

 formed from the connective tissue adjacent to the glandular 

 cell-aggregation. It may remain structureless, but extremely 

 flat stellate cells may also enter into its structure. They then 

 appear as delicate, rib-like thickenings of this membrane. 



Fir;. 26. — Tubular glands from the large intes- 

 tine of the Guinea-pig. At a, a gland with the 

 membrana propria showing in places ; at />, escape 

 of the contents through a rent in the latter. 



