INTRODUCTION 9 



fatal to them after germination. The active cells of the 

 great majority of bacteria will be killed in ten minutes 

 by a temperature of 50 to 60 C., or in five minutes by a 

 temperature of 70 C., although the dry spores of Bacillus 

 anthracis succumb only after heating for three hours at 

 140 C.* 



During the period of nearly complete dryness seeds and 

 spores are still alive, but the evidences of life are extremely 

 difficult to detect. Respiration goes on very feebly indeed 

 in air-dry seeds, yet that these seeds do respire is claimed 

 by Kolkwitz f as the result of refined methods of collecting 

 and measuring small quantities of carbon-dioxide; but 

 seeds containing still less water respire even less, and with 

 no constitutional water all respiration ceases. 



Since water is in itself lifeless, its presence or absence is 

 merely a condition which makes life possible or the reverse. 

 Life may be resident in some other of the chemical com- 

 pounds composing protoplasm, but it will manifest itself 

 only when w r ater is present in sufficient amount. Although 

 the ability to form crystals of the characteristic size, form, 

 and color resides in molecules of copper sulphate and not in 

 molecules of water, no copper sulphate crystals will form 

 until CuS0 4 molecules are accompanied by a sufficient num- 

 ber of water molecules to make the crystalline structure a 

 physical possibility. Another comparison, if not pressed 

 too far, may also assist in emphasizing and elucidating 

 this matter. The living protoplasm deprived of water may 

 be likened to the disconnected parts of a machine; it may 

 be heated or chilled or subjected to other kinds of harsh 

 treatment without greatly, if at all, affecting it; but set 

 up the machine, furnish it with energy, and it will work- 

 give an abundance of water to the protoplasm so that 

 it may set itself up into a machine, allow it to furnish 

 itself with energy, and it will work. But though water 

 is indispensable to the carrying on of the vital func- 



* Fischer. Vorlesungen uber Bakterein, Jena, -1897, p. 72. English trans, 

 by Jones, Structure and functions of bacteria. Oxford, 1900, p. 76. 



t Kolkwitz, R. f'ber die Athmung ruhender Samen. Ber. d. D. Bot* 

 Ges., Bd. XIX., 1901. 



