180 Journal of A gricultural Research voi. ix, No. 6 
This is a beautiful explanation and the work of Schneider and Havens 
tends to prove this theory. If adrenalin is the primary factor concerned 
in increasing the number of red corpuscles, hemoglobin, etc., we fail to 
understand why an increase in these factors did not result in the pig. 
CHANGES IN THE DIFFERENTIAE COUNT 
The changes in the percentage of the different kinds of leucocytes 
can be explained on the theory of rapid aging of the leucocytes due to 
increased wear. Cells grow old under physiological conditions; it is dif¬ 
ficult to follow all of the various stages, because every transition form is 
not available for presentation, because some of the stages are passed over 
too quickly, or because certain stages in the life history of different cell 
types may be very similar to each other. Transitional forms may be met 
with which can not be named, because nomenclature itself is incomplete. 
The sign? of old age in a cell are (4, p. 18): (1) The cell body becomes 
relatively larger; (2) the nucleus becomes spherical and relatively 
smaller; and (3) the nucleus becomes indented and polymorphous. 
A cell with a round single nucleus is younger than a cell with a poly¬ 
morphous nucleus. In the blood of the pig, following muscular exercise 
and exposure to the sun’s heat, we find a decrease in the mononuclear 
elements and an increase in the polymorphonuclear elements, showing 
that the cells are becoming old faster than new cells are being produced 
or that the rate of aging in a cell has been increased. The mast cells are 
increased in numbers and the majority of these cells resemble lymphocytes 
which contain many dark granules. Gruner (4, p. 19) states that the 
lymphocyte may develop mast-cell granules when suitable conditions 
arise. Thus, we find a few of the lymphocytes which assume the form 
of mast cells and may be classed under this heading. 
Muscular exercise and increased body temperature both very likely 
play an important part in hurrying the life cycle in the leucocytes. 
VARIATIONS IN BODY TEMPERATURE 
It is quite evident that the heat-regulating mechanism in the hog is a 
very poor one. Schroeder and Mohler (8) call attention to the fact that 
the hog is an animal that is ordinarily incased in a thick layer of fat, 
which is a poor conductor of heat and in which the circulation of blood is 
very meager. Over the fat a skin is stretched in which the circulation of 
blood is relatively small; and this skin, unlike that of a man or a horse, 
does not take a prominent part in regulating the body temperature 
through the agency of radiation and perspiration. The covering of a 
hog may be regarded as an excellent means for preventing the escape of 
heat from the body rather than for regulating the temperature of the 
body; hence* we have conditions that probably permit a more rapid 
production than escape of heat. These workers also state that when the 
temperature of a number of hogs is compared the difference found is of 
