FIG. 43. Egg of the common ascaris (Ascaris lumbricoides) of man, as found in feces. Seen with superficial focus. Greatly enlarged. (After Stiles, 1902b, p. 202. fig. 158.) FIG. 44. The same, as seen with median focus. Greatly enlarged. (After Stiles, 1902b, p. 202, fig. 159.)

FIGS. 45-54. Embryology of the common ascaris (Ascaris lumbricoides) of man, showing the changes undergone by the egg after being discharged in the feces. (After Leuckart, 1867, p. 213, fig. 154.)

FIG. 55. Embryo of the common ascaris (Ascaris lumbricoides) of man, in the eggshell. (After Lueckart, 1867, p. 215, fig. 156.)

FIG. 56. Free embryo of the common ascaris (Ascaris lumbricoides) of man, casting its skin. (After Leuckart, 1867, p. 214, fig. 155.)

FIGS. 57-64. Embryology of the common pinworm (Oxyuris vermicularis) of man, showing the changes undergone by the egg while in the female worm. (After Leuckart, 1868, p. 322, fig. 191.)

FIG. 65. Embryo of the common pinworm (Oxyuris vermicularis) of man, in the eggshell, as found in fresh feces. (After Leuckart, 1868, p. 328, fig. 196.)

FIG. 66. Full-grown embryo of the common pinworm (Oxyuris vermicularis) of man, after it has escaped from the eggshell. (After Leuckart, 1868, p. 328, fig. 195.)

FIGS. 67-70. Egg of the common whipworm (Trichuris trichiura) of man, showing changes undergone while still in the female worm; fig. 70 is the stage found in fresh feces. (After Lueckart, 1868, p. 491, fig. 275)

FIGS. 71-73. Later stages of development of an allied whipworm (Trichuris affinis) of sheep and cattle, showing changes after the egg escapes in the feces. (After Leuckart, 1868, p. 494, fig. 276.)

FIG. 74. Isolated embryo of Trichuris affinis. (After Lueckart, 1868, p. 495, fig. 277.)

FIG. 75. Egg of Cochin-China diarrhea worm (Strongyloides stercoralis) found in stools. (After Thayer, 1901, pl. 9, fig. A.)

FIG. 76. Rhabditiform embryo of same, from the stools. (After Thayer, 1901, pl. 9, fig. B.)

FIG. 77. Filariform larva of same derived, by direct transformation, from a rhabditiform embryo. (After Thayer, 1901, pl. 9, fig. C.)

Figures 75 to 77 were drawn from life, as seen under Leitz, objective 7-ocular 3.

FIG. 78. Egg of the common liver fluke (Fasciola hepatica) examined shortly after it was taken from the liver of a sheep; this is the same stage that is found in human feces; at one end is seen the lid or operculum, o; near it is the segmenting ovum; the rest of the space is occupied by yolk cells which serve as food; all are granular, but only three are thus drawn. x 680. (After Thomas, 1883, p. 281, fig. 1.)

FIG. 79. Egg of the common liver fluke containing a ciliated embryo (miracidium) ready to hatch out; d, remains of food; e, cusbion of jelly-like substance; f, boring papilla; h, eye-spots; k, germinal cells. x 680. (After Thomas, 1883, p. 283, fig. 2.)

FIG. 80. Embryo of the common liver fluke (Fasciola hepatica) boring into a snail. x 370. (After Thomas, 1883, p. 285, fig. 4.)

FIG. 81. Egg of lancet fluke (Dicrocœlium lanceatum) with contained embryo. x 700. (After Leuckart, 1889, p. 379, fig. 171.)

FIG. 82. Egg of human blood fluke (Schistosomr hæmatobium) with contained embryo, passed in the urine or in the feces. x 285. (After Looss, 1896, pl. 11, fig. 112.)

FIG. 83. Egg of beef-measle tapeworm (Taenia saginata) with thick eggshell (embryophore), containing the six-hooked embryo (oncosphere) enlarged. (After Leuckart.)

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MICROSCOPIC EXAMINATION OF FECES.

No special technique is necessary. Simply take a small amount of feces, preferably from near the surface, about the size of the head of a large pin; spread this out in a drop of water on an ordinary microscopic slide and cover the preparation with a cover slip. Examine under any moderately high power, as a Zeiss 8 mm., Zeiss C, or a Bausch & Lamb one-third inch. Look carefully, with not too strong illumination, for an elongate oval egg with thin shell, and with protoplasm either unsegmented or in the early stages of segmentation. The older the feces and the warmer the weather the more advanced will be the segmentation. In case of infection with Uncinaria americana the fully developed embryo may be found within the eggshell. Be cautious not to mistake for the eggs of the Uncinaria the eggs of Ascaris lumbricoides, which have a thick gelatinous, often mammillated, covering and an unsegmented protoplasm (figs. 43-44), or the eggs (figs. 57-65), of Oxyuris vermicularis, with a thin asymmetrical shell (one side being almost straight) and containing an embryo, or the eggs of whipworms (Trichuris trichiura, more commonly known to physicians as Trichocephalus dispar), possessing a smooth, thick shell, apparently perforated at each pole, and an unsegmented protoplasm (fig. 70.)

As a rule, in fecal examination I prefer to use the thick, large, 2x3-inch slide, such as is used in examining for trichinæ, rather than the ordinary 1x3 thin "English slide." The larger slide is

not only more steadily and more easily manipulated in case one is working without a mechanical stage, but it is much cleaner to handle.

In most cases of infection with intestinal worms the simple method just described will suffice for a positive diagnosis. Before giving a negative opinion, however, I invariably make ten preparations or follow a procedure which we may call "sedimenting the feces." Experience has shown me that in cases of negative diagnosis by the simple method positive diagnosis occasionally results if the feces are washed and "sedimented."

Method of Washing and Sedimenting Feces.—Take one or two ounces of feces, fresh or dry, mix with water, and place in a large bottle, retort, jar, or any other receptacle; add enough water to make from a pint to two quarts, according to the amount of feces; shake or stir thoroughly and allow to settle; pour off the floating matter and the water down to near the sediment; repeat the washing and settling several times, or as long as any matter will float. The last time this is done use a bottle or graduate with a smaller diameter, and when the material is thoroughly settled examine the fine sediment. It will be found that the eggs have settled more numerously in the fine sediment than in the coarse material.

In case an unusual amount of large coarse material is present in the feces, it is sometimes convenient to pour the entire mass through a sieve, rejecting the portion left in the sieve; or to wash the feces in a sieve, holding the latter under water. As a rule, however, the sieve is not very useful in fecal examination.

The centifuge does not appear to be of any special value in fecal examinations.

If facilities are not at hand for making a microscopic examination, about half an ounce of either perfectly fresh feces, or of rather dry feces, may be placed in a bottle, preferably with a large neck, properly packed in a mailing case, and sent to any professional pathologist or zoologist for examination.

GROSS EXAMINATION OF FECES.

If uncinariasis is suspected and it is not practicable either to