torial plane, in some cases near the anus. Eggs deposited during segmentation, in some cases containing embryo. TYPE GENUS.-Strongylus O. F. Mueller. The sexes are separate and the digestive tract is complete. Characteristic for the family is the presence, on the tail of the male, of an umbrella-like structure, known as the caudal or "copulatory bursa," supported by a number of finger-like "rays," which may be compared to the ribs of an umbrella. In coitu, the male clasps the body of the female by means of this bursa. This family is divided into subfamilies, according to the presence of certain anatomical characters. The parasites of uncinariasis are now classified in the subfamily Strongylinæ, which, as its former name, Sclerostominæ, indicated, is characterized by the presence of a hard chitinous "buccal capsule." Subfamily Strongylina. SUBFAMILY DIAGNOSIS.-Strongylidæ : Meromyaria; mouth with more or less complete chitinous armature. Male with two equal spicules; caudal bursa with rays, the dorsomedian and dorsolateral being united in a common base. Female with two ovaries, except in Ollulanus. TYPE GENUS.-Strongylus Mueller. The subfamily Strongylinæ is in turn divided into a number of genera, of which we may mention here the following: Strongylus [Sclerostoma]; the sclerostomes, including the colic worms of horses and the kidney worms of hogs (but not the kidney worms of dogs and man); Syngamus, including the gape worms of chickens; and Uncinaria, the hookworms, including the parasite of uncinariasis. Genus Uncinaria Frölich, 1789. GENERIC DIAGNOSIS.-Strongyline: With anterior extremity curved dorsally; mouth round to oval, opening oblique, limited by a transparent border and followed by a chitinous buccal capsule; the dorsal portion of the capsule is shorter than the ventral, and is supported by a conical structure, the point of which sometimes extends into the cavity; at the base of the buccal capsule are found two ventral teeth; toward the inner free border the ventral wall bears on each side of the median line chitinous structures, lips (Uncinaria) or teeth, often recurved in shape of hooks (Agchylostoma); the inner dorsal wall may also bear lips or teeth. Oviparous, eggs with thin, transparent shell. TYPE SPECIES.-Uncinaria vulpis Frölich, 1789. The anatomical character which distinguishes the genus Uncinaria is the dorsal curvature of the anterior extremity of the body, due to the shortness of the dorsal wall of the buccal capsule and resulting in bringing the mouth into a dorsal instead of a terminal or a ventral position. This genus must undoubtedly soon be divided into several genera, and the American parasite will probably be taken as type of a distinct genus. For the present, however, it will suffice to recognize two groups, Uncinaria and Agchylostoma. FIG. 2. New World male hookworm FIG. 4. The same, enlarged to show FIG. 5. Dorsal view of anterior end of New World hookworm (Uncinaria americana): b. c., buccal cavity; c. p., cervical papillæ; d. m. t., dorsal median tooth, projecting prom dorso lat ray Ventral ray ventro lat ray inently into the buccal cavity; d. sm. l., small dorsal semilunar lip; e., esophagus; m. m., margin of mouth, the prominent oval opening seen upon high focus; p. p., papillæ; v. 8m. I., large ventral semilunar lips homologous with the ventral hooks of A. duodenale. Greatly enlarged. (After Stiles, 1902b, p. 190, fig. 123.) FIG. 6. Lateral view of anterior end of New World hookworm (Uncinaria americana): b. c., buccal cavity; d. m. t., dorsal median tooth, projecting prominently into buccal cavity; e., esophagus; m. m., margin of mouth; p. p., papillæ; v. l., ventral lancets at the base of the buccal cavity, the left lancet is seen en face, the right lancet is seen from the side. Greatly enlarged. (After Stiles, 1902b, p. 190, fig. 124.) FIG. 7. Lateral view of caudal bursa of the New World male hookworm (Uncinaria americana), showing the arrangement of the rays. Note the short dorsal lobe. Greatly enlarged. (After Stiles, 1902b, p. 190, fig. 125.) FIG. 8. The caudal end of the New World male hookworm (Uncinaria americana). The bursa is spread out to show the arrangement of the rays. Note the short dorsal lobe which is subdivided, forming two lobes; note also the indistinct ventral lobe connecting the two lateral lobes. The dorsal lobe is thrown back over the body. Greatly enlarged. (After Stiles, 1902b, p. 191, fig. 126.) [Uncinaria Frölich, 1789, sensu stricto.] DIAGNOSIS.-Uncinaria s. 1. with buccal lips. The New World Hookworm-Uncinaria Americana Stiles, 1902,of Man. (Figures 2 to 9.) SPECIFIC DIAGNOSIS.-Uncinaria: Body cylindrical, somewhat attenuated anteriorly. Buccal capsule with a dorsal pair of promi nent semilunar plates or lips, similar to U. stenocephala, and a ventral pair of slightly developed lips of the same nature; dorsal conical median tooth projects prominently into the buccal cavity, similar to Monodontus. Male, 7 to 9 mm. long; caudal bursa with short dorso-median lobe, which often appears as if it were divided into two lobes, and with prominent lateral lobes united ventrally by an indistinct ventral lobe; for rays, see figures 7-8; common base of dorsal and dorso-lateral rays very short; dorsal ray divided to its base, its two branches being prominently divergent and their tips being bipartite; spicules long and slender. Female, 9 to 11 mm. long; vulva in anterior half of body, but near equator. Eggs, ellipsoid, 64 to 76 u long by 36 to 40 u broad, in some cases partially segmented in utero, in other (rare) cases containing a fully developed embryo when oviposited. HABITAT.-Small intestine of man (Homo sapiens) in America (determined to date, for Virginia, North and South Carolina, Georgia, Florida, Alabama, Texas, Porto Rico, Cuba and Brazil). TYPE SPECIMENS.-No. 3310, B. A. I., U. S. Dept. Agric. LIFE HISTORY OF UNCINARIA AMERICANA. The life history of the American hookworm has not yet been determined in detail, but there is no reason for assuming that it will differ radically from that of Agchylostoma duodenale (see p. 364). In my first description of the worm I stated that the egg in the uterus may occasionally contain an embryo. Since making this observation on the females sent to me by Dr. Allen J. Smith I have examined hundreds of fresh eggs, but have not found any containing developed embryos. The question may therefore legitimately arise whether the females originally examined were not exposed to the air for some time before they were preserved, thus making the development of the eggs possible. If the embryo does develop in the uterus, as indicated by some of Dr. Allen J. Smith's material, such an occurrence is undoubtedly rare. |