l6l THE HISTORY OF BIOLOGY 



such extremely easily discernible elements. Thanks to the resultant structural 

 conditions, which in their main features are distinguishable even to the 

 naked eye, plants have constituted the starting-point for the study of the 

 elementary nature of living matter as a whole. And the honour of having 

 introduced this study into science is due to Malpighi, even though he may 

 have had to share it to a certain extent with another, the English physician 

 Grew. 



The results of Malpighi's investigations into the subject of vegetable 

 anatomy were, after ten years of preparation, submitted to the Royal Society 

 of London and were there published. They consist of a comparative study of 

 the anatomy of different plants, both ligneous plants and herbs. First the 

 structure of the bark is described, then that of the wood and pith, and finally 

 the buds, leaves, flowers, and fruits. The different parts of these plants are 

 composed of small "utriculi" or cells, which can be distinguished by means 

 of a magnifying-glass and which in their turn form a larger connective group. 

 The cuticle and bast of the bark, the vesicular system of the wood and its 

 fibres are analysed, special interest being devoted to the spiral vessels, whose 

 inner spiral thickening induces a comparison with the tracheal system of 

 insects, in regard not only to structure, but also to function. Upon this chance 

 similarity Malpighi now bases a universal theory of respiration applicable 

 to all living creatures — which, for all its conjectural ideas, represents a 

 shrewd guess as to the uniformity of life-phenomena in all organisms. He 

 believes that the more perfect the living beings are, the smaller their re- 

 spiratory organs are: man and the higher animals do with a pair of lungs 

 of comparatively small size, whereas fishes have numerous closely ramified 

 gills, and the tracheae of insects spread throughout the entire body, while 

 again the spiral vessels in plants develop in such quantities that they fill 

 up even the most insignificant ramifications of the individual plant. Plants, 

 he supposes, take up air out of the soil through the roots; the leaves possess 

 no openings that could serve this purpose. With regard to the significance 

 of respiration for living beings, he believes that it consists in promoting the 

 mobility and "fermentation" of the alimental juices. On the whole, fermen- 

 tation plays much the same part in Malpighi's physiological speculations 

 as "cooking" does in Aristotle's; at any rate, it constitutes an advance, in 

 spite of the indefiniteness of the idea, which was inevitable considering the 

 stage of development which chemistry had reached in those days. In con- 

 nexion with his account of the elementary constituents of plants Malpighi 

 advances a number of general physiological speculations, all intending to 

 demonstrate similarities between vegetable and animal organisms and their 

 functions. In doing so he only follows, it is true, a principle which was pecul- 

 iar to a botanist of that time and which had its origin in Cesalpino's phys- 

 iological speculations on plants, to which we shall revert later on. It is, 



