Jan. 3i f 1916 
Effects of Refrigeration on Trichinella spiralis 
845 
In view of the recent discovery by plant physiologists (see Bachmann, 
1914) that sugar in plant tissues acts in some manner to protect them 
from the injurious effects of freezing so that the same species of plant is 
able to withstand a lower temperature when its tissues are loaded with 
sugar than when they contain only small quantities of this substance, 
it is of interest to note that larval trichinae contain a high percentage 
of glycogen. 
Whatever may be the explanation of the destruction of the vitality 
of trichinae and of the changes brought about by exposure to cold, the 
investigations thus far carried out are sufficient to prove that trichinae 
when exposed to temperatures of 15 0 F. or lower undergo changes in 
their protoplasmic structure, and if the temperature is low enough and 
the exposure to cold continued long enough these changes become so 
pronounced and so well established that the vitality of all of the parasites 
is entirely destroyed. 
VARIATIONS IN VITALITY OF TRICHINA 
It is natural to expect that individual trichinae would vary in resistance 
to the effects of cold, and this was found to be the case. Some succumb 
much more quickly and at higher temperatures than others. In order 
to avoid misleading results on this account, meat was not used in the 
experiments unless heavily infested so that large numbers of trichinae 
might be available for study, considerable quantities were used, as a rule, 
for examination and for feeding tests, several test animals (four to six) 
being generally employed; and, commonly, mixed meat from several 
hogs was used so that the chances of including only feebly resistant 
trichinae in an experiment may be considered to have been reduced to a 
minimum in most cases. 
QUANTITIES OF MEAT FROZEN 
As already noted, various quantities of meat ranging from a gram or 
two up to nearly 400 pounds in weight were frozen in the various experi¬ 
ments. The rate of freezing and thawing, of course, varied with the 
quantity of meat, the change of temperature being rapid when small 
quantities, slow when large quantities were used. When very small 
quantities of meat or of fluid containing free trichinae were frozen and 
thawed within a few minutes (experiments 2, 4, 5, 6,49,50) the trichinae 
were apparently much more injuriously affected than when larger quan¬ 
tities of meat were subjected to similar temperatures for considerably 
longer periods of time. On the other hand, if the quantity of meat weighed 
half a pound or more, differences in the weight, and consequently in the 
rate of freezing and thawing, made no appreciable difference in the effect 
upon the vitality of the trichinae, as is quite evident from a comparison 
of the various experiments recorded in the tables. In short, it may be 
