Manual of surgery for students and practitioners / byWilliam Rose.

  • Rose, William, 1847-1910.
Date:
1908
Catalogue details

Licence: Public Domain Mark

Credit: Manual of surgery for students and practitioners / byWilliam Rose. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    well at 18° C, or even lower. Other forms flourish best at lower or higher temperatures than these, but they are not of pathological im- portance. Lower temperatures inhibit growth, but do not kill the bacteria unless applied for long periods. The destruction of bacteria and spores by heat has been already mentioned. Light is injurious to almost all bacteria. This is especially the case with B. tuberculosis, which in vitro is killed after a very short expo- sure to sunlight and more slowly by diffused daylight. The action seems to depend on the formation of peroxide of hydrogen in the culture medium. Many pathogenic organisms require free oxygen for their develop - ment, and are spoken of as aerobes. A few, such as the tetanus bacillus, will grow only in the complete absence of oxygen, ceasing to develop, though still remaining alive, when that gas is admitted ; such organisms are called anaerobes. Bacteria which grow best in air, but which will also grow in its absence, are called facultative anaerobes, and those which grow best under anaerobic conditions, but are capable of some growth in presence of oxygen, are called facultative aerobes. It must be pointed out that the conditions in the living body are peculiar, in that both strict aerobes and strict anaerobes are capable of growth. Further, a strict anaerobe may grow in a fluid freely exposed to air in the presence of other organisms which have a great affinity for oxygen and rapidly absorb it. In this way tetanus bacilli may flourish in superficial wounds freely open to the air if other bacteria are present. In their growth bacteria give off metabolic products which are often of great importance. The chief of these are (1) acids, such as lactic, acetic, butyric, etc. ; (2) alkalies; (3) gases, such as sulphuretted hydrogen, marsh gas, etc.; (4) pigments, such as the green colouring matter produced by B. pyocyaneus and seen in the so-called blue pus; (5) aromatic substances, such as indol, phenol, and tyrosin ; (6) alcohol and other similar bodies; (7) ferments—e.g., diastase, invertase, and a ferment allied to rennin. A more important enzyme is one resembling trypsin and having the power of peptonizing proteid material. This is produced by one of the commonest pus-producing organisms (Staphylococcus pyogenes), and plays some part in the destruc- tion of the tissues in suppuration. The presence or absence of this ferment is usually ascertained by cultivating the organism in ques- tion on gelatin or coagulated blood-serum, either of which is digested or ' liquefied ' if the enzyme is produced. (8) Certain crystallizable organic substances of definite chemical composition, allied to the vegetable alkaloids, and spoken of as ptomains. They have some poisonous properties, and were once thought to be of great impor- tance in the production of disease. (9) The true toxins have never been isolated in a state of purity, but appear to be allied in chemical composition to the albumoses, and have some features in common with the enzymes. They are intensely poisonous when injected into the blood or tissues, though innocuous (in most cases) when taken by the mouth. They are very unstable substances, being readily