VITREOUS HUMOUR. 107 



the proportion formed, and the more slowly will it 

 accumulate. When this is the state of things in all 

 the organs of the body, health and longevity result. 

 The opposite entails disease and too early death. 



155. Vitreous humour. This texture is so delicate 

 that no structure can be demonstrated in it, even if 

 examined under high powers. It contains so little 

 solid matter, that 100 parts lose by evaporation up- 

 wards of 99. The tissue, however, probably forms a 

 delicate web, in the meshes of which watery fluid is 

 retained. At an early period of development nume- 

 rous masses of bioplasm may be demonstrated in 

 every part of the mass that is to become the vitreous 

 humour, and from each one may be traced extremely 

 delicate filaments, which may be followed for some 

 distance, but are at last lost sight of from their 

 tenuity. Fibres no doubt exist which are too delicate 

 to be seen. As development advances, the adult 

 vitreous masses of bioplasm become separated from 

 one another bv an increasing extent of delicate 

 tissue, and many of them disappear. Some on the 

 surface may, however, be detected even in the adult, 

 and probably are concerned in the formation of new 

 tissue at the circumference, as well as in certain 

 changes occurring in disease, which may result in a 

 complete alteration in the character of the vitreous. 



156. The mucous tissue of the umbilical cord (the 

 jelly of Wharton) is one of the simplest forms of 

 fibrous connective tissue, and one well worthy of at- 

 tentive investigation. Like the vitreous, it contains 

 very little solid matter. Its mode of growth is inte- 

 resting, and by studying it carefully, we may obtain 

 very accurate information concerning one way in 

 which interstitial growth and expansion of a tissue in 

 every direction are provided for. In very young* 

 mucous tissue oval masses of bioplasm are seen ar- 

 ranged round small circular spaces. They divide and 

 subdivide, and move in a direction outwards from the 



