Volume 1

House-flies and how they spread disease / by C.G. Hewitt.

  • Hewitt, C. Gordon (Charles Gordon), 1885-1920.
Date:
1912
Catalogue details

Licence: Public Domain Mark

Credit: House-flies and how they spread disease / by C.G. Hewitt. Source: Wellcome Collection.

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    the body of the fly than any other set of organs. It consists of three parts; the spiracles or breathing pores situated on the sides of the body, air-sacs and air-tubes or tracheae. A large pair of spiracles (ci.th.) is situated over the bases of the first pair of legs. These spiracles supply air to the following: a set of air-sacs which fill up the vacant space in the head; a series of air-sacs in the thorax which give off* tracheae to the muscles and legs, and two large air-sacs which occupy, in some cases, almost the whole of the front end of the abdomen and give off tracheae to the viscera. Above and behind the bases of the last pair of legs is another pair of spiracles which supply air to the large muscles of the thorax in that region. In addition to these thoracic spiracles there are a number of pairs of spiracles situated at the sides of the abdominal segments. In the male there are seven pairs of abdo¬ minal spiracles but in the female I have only been able to discover five pairs. All these spiracles com¬ municate with tracheae which ramify among the intestinal organs of the abdomen. The blood system of the fly is simple. The body cavity forms a blood cavity so that all the organs and muscles etc., are bathed by the blood fluid which is colourless and contains fatty corpuscles. There is a muscular tube or ‘ heart ’ lying in a cavity immediately under the dorsal side of the abdomen. It extends from the posterior end to the anterior end of the