158 THE EFFECTS OF PARASITES ON THEIR HOSTS. 



harmlessness of the flesh we use as food. One must not of course 

 think that heat and smoke (pyroligneous acid) and salt are without 

 any effect on the parasites lurking in the flesh. On the contrary, 

 one is at once convinced that these various influences are wholly, 

 though to different degrees, hurtful to the worms ; but this also is 

 certain, that the action must attain a certain intensity and last a 

 certain time before the worms die. Trichina does not perish till 

 acted on by a temperature of from 62° to 69° C, but the temperature 

 which usually prevails in the interior of the flesh during boiling or 

 roasting is often somewhat below this, and in the case of large masses 

 or rapid cooking, is so very far from it that the interior remains 

 bloody. In such cases neither the developmental power nor the hfe 

 of the inmate could be very seriously affected. Much the same may 

 be said of other (cold) methods of smoking ; we know of many and 

 serious illnesses which have resulted from the parasites derived from 

 ham or brain-sausage. The danger of partaking of such kinds of 

 food is greater, since Trichina sometimes remains living for months 

 in masses of flesh so preserved. 



I may further take this opportunity of noting that Trichina 

 has a special and uncommon power of resisting external influences. 

 It can not only remain living for weeks in the summer time in 

 putrefying muscle, but is, to a most remarkable extent, insensitive to 

 cold or frost. During the coldest part of January (at about — 20° to 

 — 25° C.) I left a portion of trichinous flesh for three days and three 

 nights in the open air, and after thawing it in cold water, gave it 

 to a rabbit. I hardly looked for any result, and was most astonished, 

 after an interval of three weeks, to find the animal emaciated and 

 paralysed. Death ensued eight days later, and I then convinced my- 

 self that it was throughout infested with Trichince. 



Such considerations make it probable that the facts established in 

 the case of Trichince cannot be directly applied to other worms. In- 

 deed, Cysticerci are killed by a temperature of 50° C.,^ and therefore 

 much sooner than the Trichince. Their possible length of life in pre- 

 served foods is also shorter, rarely exceeding four or five weeks. But 

 there is here also sufficient possibility of- infection, which is indeed 

 easy enough in the case of Taenia saginata, since beef is often eaten 

 in a half-raw state, even after cooking. 



To allay the apprehensions of our reader, we must not forget to men- 

 tion that infection through the medium of boiled or roasted flesh is on 

 the whole rare, since in the great majority of cases the parasites are killed 

 by the ordinary culinary treatment. This is as true of Trichina as of 



' This is the result of Perronoito'a experiments, which agrefe with some which I have 

 lately made, Lewis fixed the necessary temperature at 62-5 C, Pellizari even at 67 '5 C. 



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