of the small trichostrongyle, Trichostrongylus axei, from the stomach 
of the horse, is 100 to 112 microns long by 63 microns wide, according 
to most writers; Wolffhuegel says the eggs from Argentine specimens 
Fig. 46. Ascaris equorum. Eggs, x 130. From Railliet, 1893. 
are 80 microns long by 25 microns wide, a discrepancy that calls for 
further investigation. 
The egg of the horse lungworm, Dictyocaulus arnfieldi (Fig. 45) is 
80 to 100 microns long by 50 to 60 microns wide and contains an em¬ 
bryo when deposited. These eggs hatch in the lungs and the larvae 
ascend the trachea, passing out in the manure. The larvae (Fig. 45) 
Fig. 47. Oxyuris equi. Eggs, x 200. From Railliet, 1893. 
are 400 to 490 microns long by 14 to 18 microns wide, with a thin 
transparent caudal appendix. 
The eggs of the horse ascarid, Ascaris equorum (Fig. 46) are 
almost globular, 90 to 100 microns in diameter, and are not segmenting 
when deposited. The egg of the pinworm, Oxyuris equi (Fig. 47), is 
85 to 95 microns long by 40 to 45 microns wide, asymmetrical, some¬ 
what flattened on one side, and provided with a clearly defined struc¬ 
ture resembling an operculum or lid at one end. The eggs of the 
viviparous pinworm of the horse, Probstmayria vivipara, a species oc¬ 
curring in the United States, Europe and elsewhere, are elongate oval, 
58 to 100 microns long by 40 to 75 microns wide. 
48 
