KEY* FOR DIAGNOSIS OP HUMAN HELMINTHS 43 



TT. Length of buccal cavity almost equal to diameter of body. 

 Ancylostoma duodenale* or Necator americanus (Plate VI, 

 Fig. 10). Expansion at the base of buccal cavity; 

 genital anlage only 4/i to 5ju in length. 



C. Eggs in urine. 



Schistosoma haematobium (Plate V, Fig. 3). Large ter- 

 minal spine; contain fully developed miracidium; 120/z 

 to 150/i by 40/Lt to 60/i. 



D. Eggs in Sputum. 



Paragonimus westermanii^ (Plate V, Fig. 5). Operculate: 

 brownish or yellowish brown in color; contains fertilized 

 ovum surrounded by yolk cells; 80/i to 100/i by 52/z to 75/* 



E. Eggs in Feces. 



I. Operculum present. 



a. Eggs under 40ju in length; contain a fully developed 

 miracidium. 



1. Operculum sharply defined with shell projecting 



slightly behind its edge. 



(a) OpisthorcMs felineus%. Size of egg 30/t by 



11/z. 



(b) Clonorchis sinensisl (Plate V, Fig. 6). 



Average size of egg, 29/x by 16/t. 



(c) Clonorchis endemicus%. Average size of 



eggs 2Qn by 17/z. 



2. Operculum not sharply defined, the. shape being 



regularly oval, 

 (a) Egg brownish with thick shell. 



Heterophyes heterophyes. Average size of 

 eggs 30/z by 17/x. 



* Diagnosis in the case of the hookworms is usually made from 

 eggs in the stools. In old samples sometimes the eggs will have had 

 time to hatch and then the larvae must be carefully distinguished 

 from those of Strongyloides stercoralis. 



t Eggs of this form are also found in feces from swallowing of 

 sputum by the patient. 



t It is difficult if not impossible in the present state of our knowl- 

 edge to distinguish these three species by their eggs. Since their 

 geographical distribution differs, the locality from which the patient 

 comes will usually give a clue to the specific identity of the worms. 



