With the hearty coöperation of the citizens,--physicians and laymen alike,--the fight was waged and long before frost or any near approach thereto the disease was stamped out,--a thing unheard of in previous epidemics. The total loss of life was four hundred and sixty--about 11 per cent as great as that from the comparable epidemic of 1878. If the disease had been promptly recognized and combated with the energy which marked the fight later in the summer, the outbreak would have made little headway and the great proportion of these lives would have been saved. CHAPTER IX ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA (Continued) INSECTS AND TRYPANOSOMIASES By trypanosomiasis is meant a condition of animal parasitism, common to man and the lower animals, in which trypanosomes, peculiar flagellate protozoa, infest the blood. Depending upon the species, they may be harmless, producing no appreciable ill-effect, or pathogenic, giving rise to conditions of disease. A number of these are known to be transferred by insects. In order that we may consider more fully the developmental stage of these parasites within their insect host, it is necessary that we describe briefly the structure of the blood-inhabiting stage. [Illustration: 136. Trypanosoma brucei. After Bruce.] The trypanosomes are elongated, usually pointed, flagellated protozoa (fig. 136) in which the single flagellum, bent under the body, forms the outer limit of a delicate undulating membrane. It arises near one end of the organism from a minute centrosome-like body which is known as the blepheroplast, and at the opposite end extends for a greater or less distance as a free flagellum. Enclosing, or close beside the blepheroplast is the small kinetonucleus. The principal nucleus, round or oval in form, is situated near the center of the body. Asexual reproductions occurs in this stage, by longitudinal fission, the nucleus and the blepheroplast dividing independently of one another. From the blepheroplast of one of the daughter cells a new flagellum is formed. Among the pathogenic species are to be found the causative organisms of some of the most serious diseases of domestic animals and even of man. It is probable that these pathogenic species secrete a specific poison. The majority of them are tropical in distribution. Though we are concerned especially with the species which infest man, we shall first consider two of the trypanosomes of lower animals, known long before any of those of man had been found. FLEAS AND LICE AS CARRIERS OF TRYPANOSOMA LEWISI.--_Trypanosoma lewisi_, the first mammalian trypanosome known, is to be found in the blood of wild rats. Like its host, it appears to be cosmopolitan in distribution, having been reported from several localities in the United States, Brazil, Argentine, England, Germany, France, Italy, Russia, Asia and Africa.