94 



Thirty-seventh day. 



(1) Check. — No record. 



(2) Grape >! I (gar. — No record. 



(3) Cane .'<ugar. —No crystals. No .«taiii in the agar. Tlie bacterial layer peels off 

 easily in fragments, leaving a smooth, clean agar surface. This layer is not sticky or 

 elastic, and dissolves with difficulty in water, V)reaking up into rather coarse frag- 

 ments. Examined under the microscope, it consists of zooglcea}, single rods, doublets, 

 and chains. The latter are 50 to 100 jti- long. 



.SUMMAKY OF RESULTS WITH SUGAR AGARS. 



(1) Z^-. Jiyacinth! grew without retardation on the check tubes, and 

 the surface was always smooth. 



(2) Addition of per cent grape .sugar retarded growth. Finalh' 

 growth was more abundant than in the check tubes, and the surface 

 was areolated. 



(3) Addition of LT per cent grape sugar retarded growth for a longer 

 time. This was linally more abundant than in the check tubes, and its 

 surface was areolated. 



(4) Addition of 23 per cent grape sugar entirely prevented growth. 



(5) Addition of 9 per cent cane sugar did not retard grow^th, and 

 after a few days greatly stimulated it. The surface was wrinkled or 

 finely roughened. 



(6) Addition of 17 per cent cane sugar retarded growth. This 

 finally became more copious than in the check tube, but it was never 

 as abundant as on the 9 per cent cune-sugar agar. The surface was 

 wrinkled. 



(7) Addition of 23 per cent cane-sugar agar retarded growth for a 

 longer time, but did not prevent it. The surface was areolated or 

 shagreened. 



(8) Addition of 9 per cent acid fructose {Schering's diabetine) 

 entirely prevented growth. When the lactic acid was neutralized by 

 caustic soda growth ensued, but was retarded for some time. In the 

 end it was very abundant. 



Some interesting comparisons were obtained from concomitant cul- 

 tures of /-^y. cain2)estri% Ps. phwitoU^ and 1\. stewarti. 



(1) On the check or sugar-free agar all three grew without retarda- 

 tion, and did as well as Ps. kyacinthi. This agar was not stained 

 brown and no crystals were formed, but the superficial white chemical 

 film appeared whichever organism was used. This film also failed to 

 appear on the sugar agars. whichever germ was u.sed. In the check 

 tubes of each the slime was feebly alkaline at first and finalh' became 

 strongly alkaline. On the contrary, with grape sugar or cane sugar, 

 the reaction of the slime changed very slowly from alkaline to acid, 

 whichever organism was used. All four invert cane sugar. All are 

 alike in producing a small amount of non-volatile acid when grown on 



