290 
PHYSIOLOGY. 
BOOK II. 
amongst the indifferent vegetable substances, along with 
starch, gum, sugar, &c. It is only lately that Reade has 
endeavoured to earn the merit of analysing the different 
forms of organised vegetable substances when separated, but 
I doubt whether any thing available for science has resulted 
therefrom. I will, however, in no wise intimate that Mr. 
Reade has not made use of really isolated spiral vessels in 
his analysis, since he expressly asserts it; but he does not 
once mention the remotest attempt to separate the interior 
matter from the cells and vessels, which necessarily must have 
been done if any value were to be attached to the result of 
the elementary analysis. 
“ This question arises with every one who knows that 
the greater part of vegetable tissue consists of a pellucid 
membrane, and the formations deposited on its inner 
surface: Are this membrane and the subsequent deposits 
formed of the same chemical substance ? In fact, as we know 
from Mohl and Meyen that the increased thickness of the 
walls of cells consists of several layers, that even the spiral 
fibres are composed of an original fibre, and a subsequently 
deposited covering surrounding it, which I have found con- 
firmed in innumerable instances, the further question arises 
whether both the single layers of incrustation, and the 
(additional ?) parts of the spiral fibres, are not different from 
each other. As there can be no mechanical separation of 
such closely combined and microscopic parts, nothing can be 
done further than to superadd to chemical examination the 
use of the microscope, and by this means to observe the 
action of chemical reagents on the different elementary parts 
of the vegetable structure. 
“ I. I had made fine sections of an internodium of Arundo 
Donax an inch in diameter, and boiled them for some minutes 
in a solution of caustic potash. On bringing the section 
again under the microscope I was surprised by a peculiar 
appearance. A few ringed and spiral vessels were cut through, 
so that one could plainly see the section of their very thick 
fibre. By the boiling in caustic potash the spiral vessel was 
acted upon in its different parts in a very peculiar manner. 
The exterior enveloping membrane (the original wall of the 
