Nov. 25. 1918 Observations and Experiments on Intestinal Trichince 475 



It would therefore seem that it is not the high temperature which is 

 responsibloffor the rapid molting of the larvae, but that it merely hastens 

 the process commenced in the small intestine. Larvae which by their 

 behavior appear to have escaped the intestinal influences do not molt 

 even under a favorable temperature. 



SURVIVAL OF INTESTINAL TRICHINA OUTSIDE OF THE HOST 



One-day-old intestinal trichinae are sensitive to the sudden change of 

 environment and die within a few hours after their transfer from the 

 intestine to physiological salt solution, either by a gradual process of 

 disintegration in which case there is a dissolution of the worm progressing 

 from one end to the other, or else they become rigid and begin to under<70 

 granular degeneration without dissolution. It was found that such 

 parasites do not even survive for 24 hours in a refrigerator at a tempera- 

 ture of about 10° C. Two-day-old intestinal trichinae are not quite so 

 sensitive and may be kept alive for 24 hours at 10° C. but not much 

 longer. In 3-day-old intestinal parasites the resistance is greater. 

 They have been kept alive in a refrigerator for two days, though at 

 room temperature they succumbed earlier. Four-day-old and older in- 

 testinal trichinae may be kept alive without difficulty for several days 

 at a low temperature. Thus after development has actually begun in 

 the intestine the tolerance to unfavorable conditions increases in pro- 

 portion to the age of the parasite. The larvae before they have been 

 affected by their presence in the intestine are highly resistant to unfavor- 

 able conditions. On the other hand the youngest intestinal forms, 

 shortly after the resumption of growth and morphogenesis, can not 

 withstand abrupt changes which interfere with their developmental 

 processes. The sexually mature forms again pass into a condition of 

 relative stability which is accompanied by an increase in the power of 

 resistance to unfavorable surroundings. 



These observations are in harmony with the observations on the sur- 

 vival of the intestinal trichinae after the death of their host. The writer 

 found that within about 12 hours after the death of the host i-or 2-day-old 

 intestinal trichinae usually perish, though occasionally a few may remain 

 alive. They lose their hold on the mucosa and lie free in the lumen of 

 the intestine where they undergo granular degeneration. Older intesti- 

 nal trichinae survive for a longer period, since they have been found still 

 alive after the host had already begun to undergo decided putrefactive 

 changes. 



SPONTANEOUS DISINTEGRATION OF INTESTINAL LARV^ IN VITRO 



In the course of the observations on the parasites removed from the 

 intestine after artificial infection it was noted that when the larvae are 

 kept in salt solution at room temperature some of them begin to disinte- 

 grate spontaneously. In fact the writer observed on several occasions 



