34 METHODS OF EXAMINING FECES FOR PARASITISM. 



which the use of the smear method would demand. I find that 

 the careful examination of a slide not uncommonly takes 9 or 10 

 minutes. Garrison, Ransom, and Stevenson (1903a) state that the 

 examination of 100 preparations is an average day's work for one 

 person. This is a little over four minutes for each preparation. 

 Stiles (1909) states that a thorough examination of 10 slides will 

 take 40 to 60 minutes, or 4 to G minutes for each preparation. Dock 

 and Bass (1910) claim to look over an ordinary slide thoroughly 

 in 2 to 4 minutes. If one slide prepared by the writers method 

 be considered as equivalent to 4 smear preparations, and experi- 

 ence shows that it is much better than this, then it will save time 

 to spend 8 minutes in obtaining a sediment and 8 more in examin- 

 ing 2 preparations made from this sediment, rather than spend 82 

 minutes examining 8 smear preparations. Where positive infor- 

 mation as to parasitic infection is desired, the best methods and 

 the time necessary for these methods are abundantly warranted. 

 Dock and Bass (1910) state that Gage and Bass, in the examination 

 of the feces of 315 students, found only 47 per cent of the cases of 

 intestinal parasitism by the smear method, the remaining 53 per cent 

 being found by the use of centrifuge methods. They note cases where 

 the examination of 25 smear preparations failed to show infection, 

 although the existence of infection in these cases was demonstrated 

 by preparations made after sedimenting and centrifuging. 



Only in those cases where the necessary apparatus for better meth- 

 ods is not available, or where evidence of heavy infection is sought 

 for with a view to immediate medical treatment, would the writer 

 consider the routine use of the crude smear method warranted. In 

 exceptional cases its use might be warranted in examining one or 

 two slides for specific infection where there is likelihood of the 

 infection being heavy enough to be promptly discovered by this 

 method. 



ECONOMY OF METHOD. 



If the time of a physician, veterinarian, or scientist is of any value, 

 then the smear method is not even more economical than the writer's 

 method. The centrifuge is a thing which the workers just mentioned 

 should have for purposes other than fecal examinations, and the only 

 additional pieces of apparatus required the screens are inexpensive 

 and durable. 



CONCLUSION. 



The method of examining feces for evidences of parasitism which 

 consists in putting the feces through a process of thorough shaking. 

 sieving, sedimenting, and centrifuging appears, from a theoretical 

 standpoint and in actual experience, to give the best results in the 

 shortest time and with a minimum financial expenditure when the 

 value of time saved is considered. It is therefore advocated as a 

 practical routine method of examining feces of all sorts. 



