The Cell as the unit of life, and other lectures / edited by R.T. Hewlett ; An introduction to biology by the late A. Macfadyen.

  • Macfayden, Allan, 1860-1907
Date:
1908
Catalogue details

Licence: In copyright

Credit: The Cell as the unit of life, and other lectures / edited by R.T. Hewlett ; An introduction to biology by the late A. Macfadyen. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    takes place, and at 600 atmospheres the virulence of the anthrax bacillus remains unimpaired. Of the physical agents that affect bacterial life tempera- ture is the most important. Temperature profoundly influences the activity of bacteria. It may favour or hinder their growth, or it may put an end to their life. If we regard temperature in the first instance as a favouring agent, very striking differences are to be noted. A general rule- | cannot be laid down for the bacteria as a class, as each I species has its own conditions of temperature under which j its vital processes are most actively manifested. The ; bacteria show a most remarkable range of temperature ^ under which their growth is possible, extending from zero j to 70° C. If we begin at the bottom of the scale we- find organisms are to be met with in water and in, ' soil that are capable of growth and development at zero Centigrade. Amongst these are certain species of phos- : phorescent bacteria which continue to emit light even at ] this low temperatm-e. At the Jenner Institute we have met with organisms growing and developing at 1° to 4° C. ^ The vast majority of interest to us find, however, the best conditions for their growth from 15° up to 37° C. Each species has a minimum, an optimum, and a maximum temperature at which it will develop. It is important in studying any given species that the optimum temperature for development be ascertained, and that this temperature be maintained. In this respect we can distinguish three broad groups. The first group includes those for which j the optimum temperature is from 15° to 20° C. The second group includes the parasitic forms, viz. those which grow in the living body and for which the optimum I