Stephen Hales, a Reply to Criticism. 29 
the animal can be sustained by the aereal particles remaining after 
the candle has gone out.” 
It is interesting to find Mayow saying (p. 195) that “ not even 
plants can grow in earth the access of air to which is shut off ... . 
It is clear that even the very plants seem to have some need of 
breathing, some need of drawing air into themselves.” 
It is certain that Hales was acquainted with Mayow’s experi¬ 
ments since he repeated them as described in Vegetable Staticks 
(1727), p. 244. After speaking of animal respiration he goes on: 
“ And nature seems to make use of the like artifice in vegetables, 
where we find that air is freely drawn in; not only with the principal 
fund of nourishment at the root but also through several parts of 
the body of the vegetable above ground,” and so into the minute 
vessels “ where being intimately united with the sulphureous, saline 
and other particles, it forms the nutritive ductile matter 1 out of which 
all the parts of vegetables do grow.” 
It would be unreasonable to ask for clearer evidence of my 
assertion that Hales did not distinguish between respiration and 
assimilation. 2 
Poster points out how Mayow “ saw that igneo-aerial particles, 
i.e., atoms of oxygen ” were “ essential for all the chemical changes 
on which life depends.” He knew that food was also necessary for 
these vital processes. Whether he made any sharp line of distinc¬ 
tion between the two, I do not know, but in any case Hales did not. 
1 Italics mine. 
2 Wiesner has pointed out (Jan Ingen-Housz, sein Leben, &c., 1905) that 
in 1838 Meyen and Dutrochet were still striving to make clear to the world 
the difference between assimilation and respiration in plants. 
