190 DK. BEALE, ON THE TISSUES. 



but " fibrous tissue " was to be seen where we now know 

 numerous tubes and cells and vessels are actually to be 

 demonstrated. By immersing a delicate preparation in 

 water, the appearance of the presence of a large quantity of 

 fibrous or connective tissue could often be produced. 



These specimens would serve to show the great importance 

 of preparing tissues ; for it had been clearly proved that many 

 structures ordinarily invisible may be demonstrated most 

 distinctly by certain special processes. Illustrations might 

 have been taken from almost any other tissues of the higher 

 animals, or from the lower animals or plants ; but those 

 which seemed to bear most directly upon that department of 

 microscopical inquiry, which was of the greatest interest to 

 practitioners of medicine had been chosen. 



Minute size of living particles. — When we attempt to ex- 

 amine the structure of the simplest forms of living beings, we 

 cannot but regard the extreme minuteness of many inde- 

 pendent organisms which live, and grow, and increase their 

 kind, with the utmost astonishment. So also, in all other 

 living beings, the actual living particles by which the active 

 changes are eflfected are, there is reason to believe, far too 

 small to be seen. The smallest organisms and living par- 

 ticles which can be distinguished by the highest power yet 

 made (1700 diameters) had been growing probably for a long 

 time before they were large enough to be seen. 



Structure and growth of living particles. — Of the structure 

 of such organisms and particles, we have as yet learnt nothing 

 by direct observation ; but from carefully investigating the 

 structure of larger bodies closely allied to these, as ordinary 

 mildew, for instance, some conclusions as to the manner in 

 which growth takes place may be arrived at. 



Growth in all living structures occurs in the same manner ; 

 the matter to be animated passes in the same direction in all ; 

 the living particles invariably pass through certain stages of 

 existence, and end by giving rise to material totally different 

 in composition from the living particles. This may be further 

 altered, but it cannot reassume its former characters, pro- 

 perties, or powers. The differences in the results of the life 

 of different living organisms depend upon their powers, which 

 they have derived from their predecessors. 



Living particles cannot be distinguished from each other 

 by microscopical examination, and, in consequence, it is utterly 

 impossible, from the structure of a living particle, to predicate 

 its office, or the results of its living, nor can we thus tell 

 whether it has belonged to one of the lowest or highest 

 organisms, to an animal or to a plant. 



