32 



The Mechanism by Means of which the Flea might Infect a 

 Healthy Animal. 4 " 



The blood is sucked up from the wound made by the 

 pricker. This structure is composed of three parts, the epi- 



FIG. 13. 



Diagrammatic mesial sectional view of Xenopsylla cheopis 

 (from Eeport of Commission for Investigation of Plague). 

 1, Maxillary palp. 2, Maxilla. 3, Epipharynx. 4, Mandi- 

 bles. 5, Labium. 6, Undivided portion of labium. 7, Basal 

 portion of labium. 8, Basal portion of mandibles. 9, Salivary- 

 pump. 10, Hypopharynx. 11, Salivary duct. 12, Aspi- 

 ratory pharynx. 13, Muscles operating the aspiratory 

 pharynx. 14, Supraresophageal ganglion. 15, Suboeso- 

 phageal ganglion. 16, Salivary glands. 17, Gizzard. 18, 

 Stomach. 19, Malpighian tubules. 20, Rectum. 21, 

 Rectal glands. 22, Claspers. 23, Pygidium. 24, Ante- 

 idial bristle. 25, Termination of dorsal contour of 



pyg 



epipharynx. 26. Mouth. 27, Ligament. 



pharynx and the two mandibles (Fig. 14 (5, 10, 10') ). The 

 apposition of the three forms a fine tube, shown in cross 

 section in Fig. 15, up which the blood is drawn and passed 



4 In dealing with the agency of fleas in the spread of plague, I shall 

 draw largely upon the work accomplished during the last few years by 

 the Commission for the Investigation of Plague in India, with which I 

 have had the honour to be associated. The reports of the Commission 

 have been published as special numbers of the Journal of Hygiene, 1906 

 to 1912. 



