341 
Similar conclusions have been reached by Marfan (66). According 
to this author the enzymes in general can not withstand a tempera- 
ture higher than 70° C., so that by heating milk to deprive it of its 
bacteria, we also deprive it of those ferments which probably exer- 
cise a favorable influence on nutrition. He is of the opinion, how- 
ever, that this is not sufficient ground for doing away with the prac- 
tice of sterilizing milk by heat. In this connection Rosenau has 
recently made the important observation that the pathogenic 
bacteria commonly found in milk are either killed or rendered inert 
by exposure to 60° C. for twenty minutes, see Hyg. Lab. Bull. No. 42. 
Bokorny (67) has also pointed out that between protoplasm and 
the enzymes there are certain striking similarities. Toward temper- 
ature, he says, it has long been known that the enzymes conduct 
themselves like protoplasm. His table, setting forth these analo- 
gies so far as the influence of temperature and light are concerned, 
is given in the following : 
Name of protoplasm or enzyme. 
Action of temperature, light, etc. 
Protoplasm of bacteria and fungi ... 
Yeast 
Lower plants and animals. 
Zymase (yeast) 
Maltase or glucase 
Invertase (from yeast) 
Diastase (of malt) 
Emulsin 
Myrosin 
Pepsin (from the stomach) 
Trypsin (from pancreas) . . 
Papain (vegetable trypsin) 
Rennin 
Catalase (Loew) 
Laccase (Bertrand) 
Nageli found the spores of bacillus subtilis could be heated 11 
hours in boiling water without showing the slightest damage. 
In the vegetative state this organism is largely destroyed by 
heating to 55°-60° C. 
Light tends to destroy many bacteria. 
Direct sunlight destroys by long exposure. 
A temperature of 25°-30° C. best for the development of yeast. 
Young vegetative yeast-cells are killed at 50°-60°C., spores at 
60°-65° C. In the dry state yeast withstands 125° C. 
Spirogyra killed in water at 45°-50°.a Many algae live in the 
Carlsbad thermal springs, temperature 53° C. Some forms of 
algae have been found in thermal springs having a temperature 
of 85° C. 
Salt-water amoebas are killed at 35° C.; fresh- water amoebas at 
40°-45° C. 
Strong light is harmful. 
Optimum temperature, 25° C.; loses activity at 0° C. and is de- 
stroyed at 53° C. 
Yeast maltase destroyed at 55° C. Maize maltase acts best at 35° C. 
Qui ckly destroyed when moist at 70°C, and at 50°C. when heated a 
a long time. Optimum temperature, 31° C.; according to Kjel- 
dahl, 52°-56° C. 
Moist heat kills at 75° C, after short exposure. Dry diastase stands 
100° C. and over. Optimum temperature, 50°-55° C. 
Sunlight kills it. 
Optimum temperature, 45°-50° C.; destroyed at 70° C. In dry 
state stands 100° C. for hours. 
Inactive at 0° C.; thermal death-point, 85° C. 
In 0.2 per cent hydrochloric acid, optimum temperature, 35°-40° 
C. Death-temperature, 56°-60° C. Dry, stands 160° C. for a 
short time. 
Optimum temperature, 40° C. ; death-temperature, 69°-70° C. In 
dry state can be heated to 160° C. without harm. 
Optimum temperature, 40° C. Killed at 75° C. Dry, stands 100° C. 
Optimum temperature, 40° C. Higher than 70° C. kills quickly. 
Death-temperature, 72°-75° C. 
Optimum temperature, 20° C. Destroyed at 60°-63° C. ( Yoshida). 
Destroyed at. 70° .C. (Bertrand). 
“The water-plant Hottonia shows a maximum assimilation of carbon dioxide at 31° C. 
This is only one-fourth as strong at 50° C., and at 56° C. it ceases altogether. 
