536 THE MICROSCOPE. 



Intercellular Substance. In certain tissues the basis is 

 made up of a homogeneous matter, granular or fibrous, or 

 of a tissue composed of cells. The intercellular tissue 

 must be the cytoblastema after the cells have been formed 

 from it, and differs in quantity in different tissues; in 

 some it is very slight in quantity, so that it has been 

 overlooked ; but still the parts are held together, and this 

 must be by cytoblastema, which is proved by chemical 

 action. In epithelium and other parts, on the contrary, it 

 is in great quantity. This intercellular substance is some- 

 times formed into fibre, whether it be constituted of cyto- 

 blastema or of cells, and may exist in three conditions : 

 1st, as a homogeneous substance; 2d, as granular matter; 

 3d, as fibre. As an example of the first kind we have the 

 epidermis, and of the second the cellular tissue. 1 As hyaline 

 membrane it exists in cartilage. In some cartilages it is by 

 age developed into fibre, called cartilage fibre an example 

 is that between the vertebra ; for the part in immediate 

 connection with the bone, Professor T. Wharton Jones has 

 shown to be true cartilage. Sometimes the spaces between 

 cells have no intercellular substance, there may be instead 

 fluid or air ; such cavities may present different forms 

 they are termed intercellular passages, and are for the 

 conveyance of fluid or the passage of secretions : they exist 

 in animals and vegetables, but are more highly developed 

 in animals. In vegetables there are other cells lining 

 these intercellular passages, so as to form a regular tube, 

 with walls consisting of different coats. Cells exist in the 

 neighbourhood of these passages, and have shot out pro- 



(1) Mr. Huxley has ascertained that in all the animal tissues the so-called 

 nucleus (endoplast) is the homologue of the primordial utricle, with nucleus 

 and contents (endoplast) of the plant, the other histological elements being in- 

 variably modifications of the periplastic substance. Upon this view we find 

 that all the discrepancies which had appeared to exist between the animal and 

 vegetable structure disappear : and it becomes easy to trace the absolute identity 

 of plan in the two, the differences between them being produced merely by the 

 nature and form of the deposits in, or modifications of, the periplastic substance. 

 In both plants and animals there is but one histological element the endoplast 

 which does nothing but grow and vegetatively repeat itself; the other element 

 the periplastic substance being the subject of all the chemical and morpho- 

 logical metamorphoses in consequence of which specific tissues arise. The 

 differences between the two kingdoms are mainly, firstly, That in the plant the 

 endoplast grows, and, as the primordial utricle, attains a large comparative size, 

 while in the animal the endoplast remains small, the principal bulk of its tissues 

 being formed by the periplastic substance; and secondly, In the nature of the 

 chemical changes which take place in the periplastic substance in each case. 



