52 GUIDE TO THE STUDY 



Key to Parasite Eggs in Human Feces 



A. Eggs are round or slightly oval. 



B. Slightly oval with finely honeycombed surface; 65 to 75m in 

 diameter. Common in cat, very rare in man. 



Toxocara mystax 



BB. Surface of egg not honeycombed ; contains a six-hooked embryo. 

 C. Eggs isolated. 



D. Brown or brownish in color with thick, radially 

 striated capsule or embryophore; 30 to 40m in 



diameter Taenia solium 



Tcenia saginata 

 DD. Colorless with thin membranous inner shell, unstriated, 

 separated from very thin outer membrane by a 

 transparent, semifluid clear substance. 



E. 30 to 60m in diameter Hymenolepis nana 



EE. 54 to 86m in diameter Hymenolepis diminuta 



CC. Eggs in rusty red packets of 12 or more. 



Dipylidium caninum 

 AA. Eggs not round, though they may be broadly oval. 



B. Broadly oval, long axis less than twice that of shortest axis. 



C. With mammellated, thick, glutinous capsule, size 50 to 80m 



long, 45 to 55m broad Ascaris lumbricoides 



CC. Without such capsule. 



D. With thick, smooth shell, size 75 to 85m, contents 

 undivided or in early segmentation stage. Common 



parasite of dog, rare in man Toxascaris limbata 



DD. With delicate lid or operculum at one end. 



E. Eggs large, exceeding 100m in length, rounded 



at both ends Fasciolopsis buski 



EE. Eggs less than 100m in length. 



F. Eggs exceeding 80m in length, broadly trun- 

 cate at opercular end. Found in sputum 

 as well as in feces. 



Paragonimus westermani 

 FF. Eggs less than 80m in length, evenly rounded 

 at ends, contents coarsely granular, mul- 

 berry-like, shell thin and light straw 



colored Diphyllobothrium latum 



BB. Eggs not broadly oval, longest axis approximately twice the length 

 of the shortest one. 

 C. Eggs more or less truncate. 



6, Schistosoma haematobium; 7, Schistosoma mansoni; 8, Tcenia saginata; 9, 

 Tcenia solium; 10, Diphyllobothrium latum; 11, Hymenolepis nana; 12, Hymenol- 

 epis diminuta; 13, Ascaris lumbricoides, without shell; 14, Ascaris lumbricoides, 

 normal; 15, Ancylostoma duodenale; 16, Necator americanus; 17, Heterodera 

 radicicola (Oxyuris incognita) ; 18, Enterobius vermicularis; 19, Trichuris trichiura; 

 20, Syphacia obvelata. (Figures 1, 3, 4, 6, 15, 16 from Looss; 8, 9, 13, 14, Neu- 

 mann and Mayer; 5, 7, 18, Cort; 2, Ward; 12, Grassi, 10 Brumpt; 11, Augustine; 

 17, Sandground; 20, Riley.) 



