THE PHYSIOLOGY OF NUTRITION 45 



the subject, some supporting the views of Ray and 

 Camerarius, some denying them in toto. It is however 

 quite unnecessary for you to trouble yourselves with 

 these controversies, in view of the fact that opposition 

 to the sexual theory gradually died out by the beginning 

 of the eighteenth century. 



THE PHYSIOLOGY OF NUTRITION 



The first fifty years of the eighteenth century were 

 practically barren of research in plant anatomy ; during 

 all that period Grew and Malpighi remained the standard 

 authorities. Some progress was made, however, in the 

 physiology of nutrition. The physicist, Mariotte, who 

 is probably well known to you as the discoverer of the 

 law of gases that bears his name, wrote a treatise, published 

 in 1717, long after his death, called Sur le sujet des Plantes, 

 in which he combats the old Aristotelian belief that the 

 chemical constituents of plants are obtained ready made 

 from the soil. Mariotte, on the contrary, held that these 

 proximate principles were manufactured in the plant 

 body, and this view was, as we have seen, the one held 

 by Malpighi, Grew, and others at the end of the preceding 

 century. Naturally the questions that chiefly interested 

 Mariotte were those concerned with the ascent of sap, 

 which he attributed to capillarity, the pressure exerted 

 by sap as evidenced by " spring bleeding/' which he 

 took to be the cause of the opening of buds and of the 

 general expansion of the developing organs. In Mariotte's 

 pages you will find the same attempt to discover homo- 

 logies between the physiological processes in plants and 

 in animals that we have recognised in all the earlier 

 writers ; the endosperm of the seed is the yolk of the 

 egg ; the latex corresponds to the arterial blood and the 

 watery sap to venous blood, and so on. To Mariotte as 

 to his successors, and also to many botanists up to the 

 time of Ray, there was a special fascination about the 



