1889.] PITBLIC DOCUMENT — No. 34. 115 



the examination by Dr. Billings of 0,008 additional hogs, 

 mostly from the Western States, showed the per cent, to be 

 somewhat less than in the first report. Only 191 out of the 

 (),0()8 were infected ; i, e., 1 in every 31.77, or 3.15 per cent. 



During October and November, 1881, I examined thor- 

 oughly the pillars of the diaphragm only from 500 hogs. 

 The results have been given by Dr. Abbott in the supple- 

 ment to the fifth annual report of the Board (page 182). Of 

 the 500 hogs, 10, or 2 per cent., were found to be trich« 

 inous. In each case nine slips of meat from one ** pillar" 

 were examined. Three of the ten cases were only slightly 

 infected. Had the examination been restricted to the first 

 three or even to the first six slips, instead of nine, the result 

 would have been negative, since the single specimen of 

 trichina observed was found in the ninth, the eighth, and 

 the ninth slips respectively in the three cases. One of the 

 specimens of meat was further tested to ascertain the pro- 

 portion of trichinae in relation to the number of slips. 

 Thirty slips in all were examined, and only five trichinae 

 were found ; so that, had the worms been evenly distributed 

 through the muscles, one woujd have found a single worm in 

 each group of six slips. The possibility of overlooking the 

 existence of trichinae in such a mild case as this, even with 

 the examination of six slips, is evident, since it cannot be 

 assumed that the worms are evenly distributed through the 

 muscle. Observation has shown repeatedly that the reverse 

 is true ; not only that difierent muscles but also that diff*er- 

 ent parts of the same muscle may be infected in very different 

 degrees. 



I have dwelt at some length upon these examinations, 

 because in nearly all subsequent examinations only six slips 

 were employed ; and it is therefore evident that some correc- 

 tion should be applied to the results, in order to satisfy the 

 probability that the trichinae of certain specimens have been 

 overlooked, owing to their infrequency and the small num- 

 ber of slips examined. It would be quite unfair to infer, 

 however, that the results which I have arrived at should 

 be corrected by adding three to every seven found by the 

 examination of six slips to be trichinous. For, in the first 

 place, I believe, from the results of other observations, com- 



