Lectures on practical pharmacy / by Barnard S. Proctor.

Date:
1873
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on practical pharmacy / by Barnard S. Proctor. Source: Wellcome Collection.

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

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    generally require to be dried, and we will first briefly consider the various appliances which have been devised for drying, together with general precautions requisite to avoid injury of the substance under treatment. Drying. In tropical climates, little else is necessary to insure satis- factory desiccation than exposure to the air and sunshine, but in our own humid climate that cannot be trusted. Warmth and moisture are the essential conditions of rapid change in organised bodies. There is a zone of temperature which may be called the vital zone, within which the functions of animal and vegetable life are possible. The freezing and the boiling points of water may be considered the limits of active life, tliough in some recent experiments by Grace Calvert, reported in the Pharmaceutical Journal of 2d September 1871, satis- factory evidence has been found that infusorial life is capable of withstanding a heat of 800° Fahr. in infusions contained in hermetically sealed tubes, capable of bearing such a pressure as is involved by subjecting watery fluids to this temperature. He experimented upon solutions of sugar and of gelatine, and infusions of hay and of putrid meat; and in all cases found that a temperature of 212° Fahr. was insufficient to destroy the infusorial life which had made its appearance by keeping those liquors in contact with the air; and that in all cases, except the solution of gelatine, they continued in diminished proportion even after 300° Fahr. had been reached but that in all cases a temperature of 400° Fahr. was sufficient to effect the total disappearance of vitality. According to these observations, the infusorial fungi are most readily destroyed, a temperature of 212° Fahr. being fatal to them; and the vibrios the least readily destroyed, their vitality continuing in solutions exposed to 300° Fahr., but not in those heated to 400° Fahr. He.also found intense cold incapable of destroying these low forms of pro- toplasmic life, a liquor containing microzima and vibrios, on being frozen and retained for twenty hours at temperatures