JANUAEY 30, 1914] 



SCIENCE 



181 



parison with the interception of incoming 

 solar radiation." 



Professor Humphreys now turns his atten- 

 tion to the observational evidence of pyrhelio- 

 metric records, such readings being functions 

 of, among other things, both the solar atmos- 

 phere and the terrestrial atmosphere. He thus 

 introduces a curve showing smoothed values 

 of the annual average pyrheliometric values, 

 and compares this with sun-spot frequency 

 values (representing solar atmospheric 

 changes) and number of volcanic eruptions 

 (representing terrestrial atmospheric changes). 

 The similarity of the last-mentioned with the 

 pyrheliometric curve leads him to write as fol- 

 lows : " Hence it appears that the dust in our 

 own atmosphere, and not the condition of the 

 sun, is the controlling factor in determining 

 the magnitudes and times of occurrence of 

 great and abrupt changes of insolation inten- 

 sity at the surface of the earth." 



The action of the dust intercepting at times 

 as much as one fifth of the direct solar radia- 

 tion leads him to inspect earth surface tem- 

 perature values to inquire whether they are 

 below normal on such occasions. The pyrhelio- 

 metric and temperature curves suggest a rela- 

 tionship, but, as he states, " the agreement is 

 so far from perfect as to force the conclusion 

 that the pyrheliograph values constitute only 

 one factor in the determination of world tem- 

 peratures." A better agreement is secured 

 when the combined effect of insolation inten- 

 sity and sun-spot influence is considered. 



The author then discusses the temperature 

 variations since 1750 as influenced by sun- 

 spots and volcanic eruptions, and indicates 

 that the disagreement in the curves of tem- 

 peratures and sun-spots is in every important 

 instance simultaneous with violent volcanic 

 eruptions. 



Limitations of space will not permit us to 

 remark on his references to the action of car- 

 bon dioxide in slightly decreasing the tem- 

 perature or to probable great changes in level. 

 Enough perhaps has been said to show that 

 Professor Humphreys, in his interesting at- 

 tempt to show " that volcanic dust must have 

 been a factor, possibly a very important one, 



in the production of many, perhaps all, past 

 climatic changes . . .," has restarted a topic 

 which will no doubt call for criticisms and 

 discussions from many quarters. 



SPECIAL ARTICLES 



THE EFFECT OF COLD UPON THE LAEVjE OF 

 TRICHINELLA SPIRALIS 



In the course of an investigation relative to 

 Trichinella spiralis^ it has been determined 

 that cold has a decided destructive effect upon 

 the encysted larvae of this parasite. Heretofore 

 it has been accepted as an established fact, 

 upon the basis, however, of insuiEcient evi- 

 dence, that low temperatures have no con- 

 siderable influence upon the vitality of the 

 larvffl of Trichinella. Although the results of 

 only a single series of the writer's experiments 

 are available at present, these results have 

 been so definite that there can be little doubt 

 as to the lethal action of cold upon Trichinella 

 larvae. The writer's experimental work thus 

 far has shown that most of the parasites sur- 

 vive when exposed for as long as six days to a 

 temperature ranging between 11° and 15° F. 

 (= — 11.70° to —9.4° C). On the other 

 hand, when exposed to a temperature in the 

 neighborhood of 0° F. (= — 17.8° C.) the 

 larvae of Trichinella quickly succumb. Only 

 one out of over 1,000 larvae examined has been 

 found to survive an exposure of six days to 

 this temperature. This was one among 275 

 isolated from a piece of trichinous meat which 

 had been kept at a temperature of about 0° F. 

 from September 27 to 30, allowed to thaw, 

 and then again kept at the same low tempera- 

 ture, October 1 to 4, a total of six days' expos- 

 ure. None was found alive among 498 larvae 

 from a piece of trichinous meat kept at about 

 0° F. September 27 to 30, allowed to thaw, 

 then exposed again to the same low terapera- 

 ture October 1 to 3, and thus exposed five days 

 in all, nor was any found alive among 233 larvae 

 from a piece of trichinous meat kept continu- 

 ously at about 0° F. for five days. Out of 301 

 larvse from trichinous meat kept at about 0° F. 

 for three days only 5 showed signs of life. 225 

 out of 366 larvae exposed for two days to a 



