CHAPTER V. 



OF CELLULAR TISSUE, REGARDED AS THE MATRIX IN WHICH 

 ALL ORGANISATION HAS BEEN CAST. 



As we observe the facts presented to us in the various parts of nature, 

 it is curious to remark how the simplest causes of observed facts are 

 often those which remain the longest unperceived. 



It is no new discovery that all the organs of animals are invested 

 by cellular tissue, even down to their smallest parts. 



It has indeed been long recognised that the membranes which form 

 the investments of the brain, nerves, vessels of all kinds, glands, 

 viscera, muscles and their fibres, and that even the skin itself are all 

 the produce of cellular tissue. 



Yet in this multitude of harmonious facts, nothing more appears 

 to have been seen than the mere facts themselves ; and no one 

 that I know of has yet perceived that cellular tissue is the universal 

 matrix of all organisation, and that without this tissue no hving body 

 could continue to exist. 



Thus when I said ^ that cellular tissue is the matrix in which all the 

 organs of living bodies have been successively formed, and that the 

 movement of fluids through it is nature's method of gradually creating 

 and developing these organs out of this tissue, I was not afraid of 

 coming upon any facts which might testify to the contrary ; for it 

 is by examining the facts themselves that the conviction is acquired 

 that every organ whatever has been formed in cellular tissue, since it is 

 everywhere invested with it even down to its smallest parts. 



Hence we see that in the natural order, both of animals and plants, 

 those living bodies whose organisation is the simplest and which are 

 consequently placed at one extremity of the order, consist only of a 

 mass of cellular tissue in which there are to be seen neither vessels, 

 nor glands nor any viscera ; whereas those bodies, whose organisation 



* Opening addreea of the course of invertebrate animals delivered in 1806, p. 33. 

 Since the year 1796, I have stated these principles in the early lessons of my course. 



