INFLUENCE OF NUTRITION ON GROWTH 133 



The walls of the mother-cell swell up, the chain is dissolved, and the endospores 

 thereby liberated. Some facts indicative of their power to resist adverse 

 influences have been given in a previous section ( 53). The spore membrane is 

 capable of swelling up, so that when the spores are placed in water each of them 

 soon appears to be surrounded by a dull halo the swollen external layer of the 

 membrane. 



109. Influence of the Mode of Nutrition on the Form of Growth. 



This factor was exhaustively described, for the bacillus in question, by HANS 

 BUCUNEU (IV.). A few of the forms of growth observed are shown in Fig. 42. 

 By employing a faintly 

 alkaline 5 per cent, solu- 

 tion of meat extract, 

 rods (as at ia) are ob- 

 tained, 0.5/4 broad and 

 6-10 p. long. If a neutral 



solution of 5 per cent, of 

 sugar and o.i per cent. 

 of meat extract be taken, 

 then the forms shown in 

 2 appear, viz., short rods 

 0.8 /* broad and only 4-6 

 p. long. Finally, in an 

 infusion prepared from 

 hay in which woody 

 stems predominate, the 

 cells (yi) have a length 

 of 12 ji and a breadth 

 of i.o p. Under all the 

 above conditions repro- 

 duction goes on with 

 vigour, the fission being 

 very rapid. The new 

 partition walls formed 

 during the operation are 

 at first so thin and so 

 faintly refractive as to 

 escape the eye in the case 

 of unstained prepara- 

 tions. If, however, a solu- 

 tion of iodine be added, 

 then the apparently 

 uniform long cells are 

 seen to be divided into 

 short cells in the manner 

 diagrammatically 

 sketched at b and c in the 

 figure. All these shapes 

 belong to the cycle of 



FIG. 42. Bacillus subtilis under various conditions of cultiva- 

 tion. For explanation see text. Magn. about 4000. (After 

 H. Buchner.) 



normal forms of growth, of strong vitality, and capable of reproduction. When, 

 however, the composition of the nutrient solution is, from the first, unfavourable 

 (e.g. a solution of o. i per cent, of asparagin or albumen, and 10 per cent, of sugar), 

 or becomes so subsequently in consequence of the excretion of injurious waste 



