194 EIGIirEENTH CENTURY. pt. 



plants breathe through the little stomata^ or mouths, disco- 

 vered by Grew (see p. 141). 



From the juices of plants Boerhaave next went on to 

 those of animals, and he decomposed in a most beautiful 

 and simple manner milk, blood, bile, and those fluids called 

 chyle and lymph which convey nourishment to the blood. 

 These he compared with the sap, gums, resins, and oils of 

 plants, and showed that animal bodies are made up of 

 altered vegetable matter, just as plants are in their turn 

 composed of matter taken from the soil and the air; and 

 he suggested that by careful experiments it would at last be 

 possible to discover exactly the materials of which all living 

 beings were made. 



Boerhaave's analyses of organic substances were very 

 rough and imperfect compared to those which are made now; 

 for you must remember that the four gases, oxygen, hydro- 

 gen, nitrogen, and carbonic acid, which we now know are the 

 chief constituents of plants, were not yet discovered. Yet 

 even these rough attempts were so interesting that students 

 crowded round the doors of his lecture-room for hours 

 before the lecture began, to secure admission ; and there can 

 be no doubt that his * Elements of Chemistry,' pubhshed in 

 1732, contained the first steps in the study of the chemistry 

 of living things. Boerhaave was also a celebrated botanist. 

 He died in 1738, and deserves always to be remembered as 

 one of the greatest teachers of the eighteenth century. 



i 



Chief Works consulted. — Brewster's 'Encyclopaedia ' — 'Boerhaave ;' 

 Cuvier, * Hist, des Sciences Naturelles ; ' Sprengel, ' Hist, de la Medi- 

 cine,' 1815 ; Burton's 'Life and Writings of Boerhaave,' 1746 ; Boer- 

 haave, 'Elements of Chemistry,' Englished by Dallowe, 1735 ; Miller's 

 'Chemistry ;' Hales' 'Essays concerning Vegetable Staticks,' 1759. 



