116 STATE BOAIID OF HEALTH. [Jan. 



plete records of which were not kept, that three such cases in 

 ton is an unusually large proportion ; and, secondly, if it 

 were certain that out of every ten tricliinous hogs three were 

 so feebly infected that nine slips must be prepared to secure 

 one trichina, there is no reason to suppose that the slip con- 

 taining the single trichina would be the seventh, eighth and 

 ninth, any more than the first, second and third ; so that, if 

 six slips were examined, the chances are that in two-thirds of 

 these cases the trichina would be found. Thus, at most, 

 there would have to be added one — not three — to each 

 seven found trichinous, in order to counterbalance the prob- 

 able oversight. But, as I have said, I believe that this is 

 much too large a correction. One to ten, or even one to 

 twenty, would probably be much nearer the reality. Sup- 

 posing, however, that for every ten found by such examina- 

 tion to be trichinous one were to be added ; even that could 

 have very little practical importance, especially when those 

 which are shown positively to be infected reach such high 

 numbers as appear in this report. It is in view of the com- 

 parative insignificance of this error that I have ventured to 

 limit my examinations to six slips, and have concluded that 

 the degree of accuracy attained was sufficient for all prac- 

 tical purposes. It is to be remembered that this series of 

 examinations has been undertaken not as an inspection of 

 pork, where the examination should be rigid and as nearly 

 absolute in its results as possible, but simply as a means of 

 finding an approximate answer to the question. What propor- 

 tion of the hogs raised in a given district are trichinous ? 



In order that the examination should be as thorough as 

 possible under these conditions, the slips were taken each 

 from a difierent part of the '' pillar," so that no considerable 

 portion of the specimen remained without inspection. The 

 six slips together weighed on the average about twelve 

 centigrams (one grain) ; they were cut in the usual manner, 

 with scissors, laid on a glass slide, and covered by a slightly 

 narrower slide of thinner glass. The cover-slide was ruled 

 lengthwise with parallel lines, slightly closer together than 

 the diameter of the field of the microscope, to aid in count- 

 ing the number of trichinae in the infected specimens. The 

 cover-slide was applied with the ruled side down ; that is, in 



