May 7,1917 
Effects of Exercise and Sun on Normal Pigs 
181 
such magnitude that they were at a loss to conclude what should be 
regarded as normal. 
There are several factors which can possibly account for the wide 
variations found in the temperature of normal hogs: (i) The condition 
of the animal—that is, the amount of fat; (2) the temperature of the 
atmosphere and the percentage of humidity. A fat hog would have a 
much higher body temperature on a hot humid day than a lean hog, and 
even on a cool day a slight variation may occur. Schroeder and Mohler 
conclude that fat hogs have a higher temperature than lean ones, and 
that a higher temperature induced by exercise or some other temporary 
cause persists longer in fat than lean. hogs. 
Since environment can cause a marked variation in the temperature 
of man, with his excellent heat-regulating mechanism, we would expect 
that similar conditions would cause a greater variation in the case of 
the pig with a poor heat-regulating mechanism. 
SUMMARY 
(1) Blood examinations in nornrnl resting pigs, covering a period of 
24 hours, may be quite uniform; but in some animals there is marked 
variation throughout the period. 
(2) Observations made upon a number of animals leads to the con¬ 
clusion that muscular exercise does not cause an increase of red cor- 
. puscles in the peripheral circulation of the pig. 
(3) Results based on only one or a few experiments may lead to wrong 
conclusions, owing to the variability in the blood of pigs. 
(4) Evidence given by work with the pig tends to confirm the theory 
of perspiration being responsible for the increase in the number of red 
corpuscles following muscular exercise in man. 
. (5) Muscular exercise in the pig is usually followed by a leucocytosis. 
(6) This leucocytosis is probably the result of muscular exercise forc¬ 
ing leucocytes into the general circulation from the tissues. 
(7) Muscular exercise leads to marked changes in the differential 
counts. The mononuclear elements are decreased, and the polymorpho¬ 
nuclear elements are increased. $he height of the curve is reached 
several hours after exercise, and the normal proportions do not return 
for many hours. 
(8) Exposure to the sun causes similar changes in the differential 
curve. 
(9) These changes under both conditions are the result of increased 
rate of aging of the leucocytes, the cells becoming older faster than 
young cells are being produced. 
(10) Muscular exercise and heat of the sun lead to a marked increase 
in body temperature. 
(11) Body temperature changes are more pronounced in fat pigs than 
lean ones, but even in pigs weighing 75 to 100 pounds marked changes 
are likely to occur. 
