COLLECTION INDEX. 23 



COLLECTION INDEX. 



The writer has had no opportunity to work out an index showing 

 (he relation of the count obtained by the writer's method to the num- 

 ber of worms present. In few cases where the feces of animals are 

 examined in this laboratory are the animals examined post-mortem 

 within a short time. In one instance. 3 grams of feces were taken 

 from the rectum of a sheep during a post-mortem examination for 

 parasites, and after treatment by the writer's method, noting the time 

 element and the amount of water used in each case which data need 

 not be given here a slide was made of one-tenth of a cubic centi- 

 meter of sediment. This slide showed 3,325 nematode eggs and em- 

 bryos. The intestines and fourth stomach showed a correspondingly 

 high degree of infection with numerous species of worms, and it was 

 impossible to determine the relation between the number of female 

 worms of any species and the number of eggs of that species under 

 the circumstances. 



In spite of the relation found by Cobb (1004) as regards flukes. 

 by Leichtenstern and by Grassi and Parona, according to Dock and 

 Bass (1910), as regards hookworms, between the number of parasites 

 present and the number of eggs in a given fecal sample, the examina- 

 tions made by the writer do not indicate that anything of the sort 

 is apt to prove of use in routine examinations for parasites in general. 

 Dock and Bass (1910) have come to similar conclusions and cite the 

 work of Ashford and King to the same effect. Not only is there 

 a certain element of chance in the detection of eggs when they are 

 present in light infections, but there are certain conditions which 

 permit of the existence of parasitism without the presence of eggs 

 in the feces to indicate it. Some of these conditions are as follows: 



(1) Infection with male nematodes will not be indicated by eggs 

 in the feces. Occasionally the only nematodes of a given species 

 which are present in an animal will be males. Such infections are 

 usually light. 



(2) The above condition will not be true of the flukes and tape- 

 worms, as they are hermaphroditic; but in the case of these worms, 

 and the nematodes also, infections which are so recent that the 

 infecting larvae have not yet reached the egg-producing stage will 

 not be indicated by eggs in the feces. Such infections may be heavy. 



(3) Egg production in female or hermaphroditic animals may be 

 interrupted in various ways. Thus tapeworms may be broken, per- 

 haps by intestinal peristalsis, at points anywhere from just back of 

 the head to just in front of the gravid proglottids. and the feces will 

 show no more eggs or proglottids until new gravid proglottids are 

 formed. Dock and Bass (1910) report that in an examination of 

 247 female Nccator americanus by Bass. 7 per cent were found to 



