Aug. 15. 1919 



Effects of Heat on Trichince 



219 



Tabi.Iv II. — Effects of continued action of temperatures below thermal death point < 



encysted trichince 



Temperature. 



Appearance of larvae after artificial digestion. 



Ap]>arently dead 



Profoundly disorganized 



Showing evidence of having been partially 



digested : 



Uncoiled ; evidently dead 



Apparently dead 



Probably dead 



Uncoiled and pale 



....do 



....do 



Results of feeding 

 experiments. 



Coiled Negativ 



Do. 

 Do. 



Do. 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 



From a practical standpoint the results of the experiments on the 

 effects of continuous heating at temperatures below the thermal death 

 point of trichinae are of comparatively^ little importance so far as con- 

 cerns the destruction of the vitality of trichinae in fresh pork by cooking. 

 Obviously, as compared to cooking at a higher temperature for a short 

 time, there would be no advantage in subjecting meat to a lower tem- 

 perature, which would require a very great lengthening of 'the period of 

 heating. If for no other reason, the probable spoiling of the meat would 

 preclude the use of such a method of destroying the vitality of the 

 parasites. In connection with the preparation of certain kinds of cured 

 pork products, however, the fact that heating at low temperatures for 

 considerable periods of time is destructive to the vitality of trichinae has 

 been put to practical use. In this case there is also another factor 

 which comes into play — namely, the destructive action of salt in hyper- 

 tonic percentages, which increases greatly as the temperature increases. 

 The question of the destruction of trichinae in cured pork by heating at 

 low temperatures will be discussed in another paper. 



CONCLUSIONS 



The vitality of the larvae of Trichindla- spiralis is quickly destroyed 

 by exposure of the parasites to a temperature of 55° C, gradually 

 attained, the result apparently of irreversible coagulation changes in the 

 protoplasm. This temperature may be considered the thermal death 

 point. 



Trichina larvae exposed to temperatures slightly below 55° C. for short 

 periods of time may recover from this exposure; but they die if exposed 

 for longer periods, recovery or death depending apparently upon whether 

 or not beginning coagulation of the protoplasm has proceeded bevond 

 a stage from v/hich a return to normal mav occur. 



