1 74 Journal of A gricultural Research v 0 i. ix, no 6 . 
II.—EFFECTS OF HEAT OF SUN 
In this series of five experiments on the effects of the sun's heat only 
the changes in the leucocytes were studied. The differential curve for a 
period of 36 to 72 hours was worked out. The results in general were 
quite similar to those obtained in the animals which were given muscular 
exercise. 
(a) Lymphocyte curve. —The lymphocytes were decreased in number, 
the height of the reduction occurred from 4.5 to 7 hours after being 
placed in the sun, and the average for. the five experiments was 6 hours. 
At this time they were decreased 5.06 to 17.01 per cent, the average 
being 11,48 per cent. After this there was a gradual return to the 
normal proportions, which took place after 15 to 48 hours, the average 
being 29 hours. The greatest change required the longest time to return 
to normal. 
(b) Polymorphonuclear curve. —The polymorphs were increased 
in numbers, the height of the reaction occurred from 4.5 to 7 hours 
after being placed in the sun, and the average for five experiments was 
6 hours. At this time they were increased 3.79 to 21.63 P er cent above 
the normal, the average increase being 11.4 per cent. After the height 
of the reaction there was an irregular return to the normal, which took 
place between 15 and 72 hours or more. The lowest change required 
the least time to return to normal. 
(c) Mononuclear curve. —There was a slight decrease in the number 
of mononuclears. The height of the reaction occurred about 6 hours 
after being placed in the sun. Following this there was a gradual 
increase to the normal proportions. This increase was quite irregular. 
In general, the behavior of these cells was quite similar to the lympho¬ 
cytes. 
(d) EosinophilE curve. —The behavior of the eosinophiles was, in 
general, very similar to this class of cells following muscular exercise. 
If the normal percentage of these cells was rather high, there was always 
a decrease, the height of the reaction occurring about 5 to 7 hours after 
being placed in the sun. Following this there was a gradual increase 
in the number of these cells, the increase running far beyond the normal 
percentage. The height of this increase was attained from 13 to 2.7 
hours after being placed in the sun. Then there was a gradual return 
to the normal percentage. If the normal percentage was low, the first 
decrease, did not occur, but there was a gradual increase until about 13 
to 27 hours after being placed in the sun, when the height of the reac¬ 
tion occurred. After this there was a gradual return to the normal 
proportions. 
