Handbook on contagious and infectious diseases in animals / issued by the Quartermaster General's Branch, General Headquarters, India.

Date:
[1944?]
Catalogue details

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: Handbook on contagious and infectious diseases in animals / issued by the Quartermaster General's Branch, General Headquarters, India. Source: Wellcome Collection.

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    HANDBOOK ON CONTAGIOUS AND INFECTIOUS ' DISEASES IN ANIMALS PART |. A FEW FACTS REGARDING MICRO-ORGANISMS. Micro-organisms, popularly referred to as microbes, germs, bacteria etc., cause contagious diseases. The symptoms seen in these diseases are the results of the invasion of the animal body by these parasites. It follows therefore that if outbreaks of contagious disease are to be dealt with and suppressed, something must be known of the life history of the micro-organisms which cause them. They are generally classified as the lowest order in the plant world but some, e.g., the protozoa belong to the animal kingdom. Structure of micro-organisms.—Bacteria appear under the microscope as pale translucent bodies; they are one-celled organisms composed of protoplasm surrounded by a membrane or skin which, in some, swells up to form a jelly-like casing. Types of organisms.—The organisms vary very much in shape and size. Some are globular or spherical in shape, and are generally known as cocci; many, on the other hand, are rod-like bodies, hence are termed bacilli; whilst others, having a spiral or corkscrew shape, are known as spirilla. Long unbranched filaments are called leptothrix, while others which branch are known by the name cladothrix. All these various shaped organisms are loosely spoken of as bacteria. Other classes of micro-organisms, are the moulds and the saccharo- mycetes or yeasts. Moulds consist of slender threads which give rise to the woolly patches often seen on various articles of food; the saccharo- -mycetes or yeasts are ovoid or sausage-shaped cells which are much larger than the bacteria proper. The protozoa referred to above cause trypanosomiasis in man and animals, the conditions known as sleeping sickness in man and ‘‘ surra ”’ ‘“nagana ’’ etc., in animals being closely allied. Size of organisms.—Most of the bacteria are on an average from ty | k ~ 95.000° 82 inch long to about five times that length. The best impression Bh : of the size of bacteria is obtained when it is stated that a 5, inch immer- sion lens (microscope) gives a magnification of nearly 2,200 diameters, | 1a