PHYSIOLOGY. 179 



quickly out of the body again by the excretions ; or when they 

 are such as admit of their qualities being entirely changed 

 by the powers of digestion in the first passages. Such excep- 

 tions, however, hardly affect the general doctrine ; which is very 

 much confirmed by this, that several vegetables which in their 

 acrid state are unfit or even noxious, by being deprived of their 

 acrimony by culture, by blanching, by drying, or by boiling, 

 are rendered quite proper : and if there shall still be exceptions 

 not to be accounted for in any of these ways, I would maintain 

 that such acrid substances are admitted and taken in as condi- 

 ments rather than as nutriments. 



" This consideration of the exclusion of acrid matters from a- 

 mong our foods is to be applied in this manner. As the acrid, 

 odorous, or sapid parts, seem for the most part to be the pecu- 

 liar matter of particular vegetables, and to be even but a small 

 portion of these, seldom diffused over the whole but deposited 

 in certain parts of them only ; and as this is more especially 

 the case in those vegetables which are taken in as food ; so we 

 from thence conclude, that besides these peculiar matters, there 

 is in the most part of vegetables a considerable quantity of 

 matter, which, for reasons to be given hereafter, is manifestly 

 in common to almost the whole of the vegetable kingdom. 

 This we shall speak of as the common matter of vegetables, 

 and having laid aside, as above, the peculiar, it is in the common 

 matter that we are necessarily led to seek the vegetable sub- 

 stance that is suited to the nourishment of the human body. 



"Whilst from this consideration it appears that a great portion 

 of vegetables is of an alimentary quality, at the same time it is 

 from daily experience evident, that certain vegetables contain a 

 greater portion of this alimentary matter than others, and that 

 certain parts of vegetables contain more of it than other parts 

 of them." M. M. 



CCXI. It is this common matter of vegetables, therefore, 

 that we are to consider here ; and we think it may be consider- 

 ed as of three kinds only, that is, oily, saccharine, and what 

 seems to be a combination of these two. " In attempting this, 

 it must, in the first place, be observed, that, contrary to what 

 others have supposed, I cannot discern that any portion of mat- 

 ter is to be found existing in any vegetables directly fitted to 



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