256 THE CELL-THEORY 



course no one denies this fact ; but of what value is it ? Is the fact 

 that a rhombohedron of calcareous spar breaks up, if pounded, into 

 minute rhombohedrons, any evidence that those minuter ones were 

 once independent, and formed the larger by their coalescence ? Is 

 the circumstance that wood itself tears up into fibres, any evidence 

 that it was formed by the coalescence of fibres ? Assuredly not ; for 

 every hand-book will tell us that these fibres are the result of a 

 metamorphosis of quite different parts. Is it not perfectly clear, that 

 the behaviour of a body under mechanical or chemical influences, is 

 simply an evidence of the disposition of the lines of greatest cohesion 

 or affinity among its particles at the time being, and bears not in the 

 slightest degree upon the question as to what these lines indicate ; 

 whether they are the remains of an ancient separation among hetero- 

 geneous parts, or the expression of a recent separation which has arisen 

 in a homogeneous whole ? So that, if the walls of the cells were really, 

 as distinct from one another as is commonly supposed, it would be no 

 argument for their vital independence : but they are not so. Von 

 Mohl has shown that, in the great majority of cases, the assumption 

 of the existence of a so-called intercellular substance, depends simply 

 on imperfect chemical investigation, that there exists no real line of 

 demarcation between one cell and another, and that wherever cells 

 have been separated, whether mechanically or chemically, there is 

 evidence that the continuous cellulose substance has been torn or 

 in some way destroyed. In young tissues — such, for instance, as the 

 cambium, or the base of a leaf, we have been quite unable to detect 

 the least evidence of the existence of any line of demarcation between 

 the cells ; the cellulose substance forms a partition between cavity 

 and cavity, which becomes evenly -blue throughout by the action of 

 sulphuric acid and iodine, and which certainly, even under the highest 

 powers, exhibits no symptom of any optical difference ; so that, in 

 this state, vegetable tissue answers pretty closely to Wolffs idea. It 

 is a homogeneous cellulose-yielding, transparent substance, containing 

 cavities, in which lie peculiar vesicular bodies, into whose composition 

 much nitrogen enters. It will be found a great aid if in the present 

 confused state of terminology the reader will accept two new denomi- 

 nations for these elementary parts, which express nothing but their 

 mutual relation. To the former, and to everything which answers 

 to it, we shall throughout the present article give the name of Periplast, 

 or periplastic substance ; to the latter, that of Endoplast. So far, then,, 

 from the utricles or cells in the plant being anatomically distinct, we 

 regard it as quite certain that that portion which corresponds with the 

 periplast, forms a continuous whole through the entire plant. 



