Aug. IS. 1919 Effects of Heat on Trichince 205 



to which they are subjected. Pure water as compared to physiological 

 salt solutions was found to be distinctly injurious, the injurious action va- 

 rying directly with the temperature. Larvae kept in distilled water at a 

 temperature of 39°-4o° C. were all dead at the end of 22 hours, while in 0.7 

 per cent solution of sodium chlorid or in Ringer's solution they lived longer, 

 although they all died within 48 hours. In distilled water at a tempera- 

 ture of 32°-33° decapsuled larvae were nearly all uncoiled at the end 

 of 48 hours, while in 0.7 per cent sodium-chlorid solution or in Ringer's 

 solution some were still alive at the end of 5 days. Similar differences 

 were observed in the case of lower temperatures. In distilled water at 

 25°-26° larvae remained alive for 4 days; in physiological salt solutions 

 at 25 °-2 7° some were still alive at the end of 13 days; in distilled water 

 kept at a temperature of about 8° only a few larvae were still alive at 

 the end of 12 days; while in physiological salt solutions at the same tem- 

 perature some larvae were still alive at the end of 50 days. 



From these observations and our general knowledge of the phenomena 

 of osmosis it would appear that the loss of salts from the tissues of the 

 worms into the water and the penetration of the water into the tissues of 

 the worms are important factors in bringing about the death of the worms 

 when kept in hypotonic media, such as distilled water. This belief is borne 

 out also by the fact, noted in a former paper (11, p. 849) and repeatedly 

 observed since that paper was written, that larvae kept in a hypotonic 

 solution until they have begun to show distinct evidence of its effects, such 

 as loosening of their coils and paling of their protoplasm, if transferred 

 to a physiological salt solution before the injurious action of the hypo- 

 tonic medium has gone too far, will usually resume a normal state of con- 

 traction and a normal or almost normal brown color. Another indication 

 that the death of decapsuled larvae kept in hypotonic solutions may be 

 dependent upon osmotic processes is that they die more quickly at high 

 than at low temperatures, which is in harmony with the fact that osmosis 

 is hastened by raising the temperature. 



Another factor or factors, however, enter into the matter, inasmuch as 

 in isotonic solutions as well as in hypotonic solutions the larvae do not 

 survive so long at high temperatures as at low temperatures. It may be 

 supposed that at the higher temperatures death of the lar\^ae kept in iso- 

 tonic and comparatively inert solutions is brought about by exhaustion 

 resulting from the greater activity of the worms and consequently more 

 rapid oxidation of their tissues than at lower temperatures. Such an 

 explanation is complicated by the fact that larval trichinae encysted in 

 the muscles of a living animal may live for many years, although con- 

 stantly subjected to a temperature at which they live only two or three 

 days when removed from their cysts and kept in salt solutions. Possibly 

 in the living animal they are kept in a relatively inactive condition 

 through the operation of factors no longer present when they are removed 



