INCUBATION 
ciple at stake, and without looking up authorities, I will state 
these temperatures for a number of animals. Of course you 
can dispute the accuracy of these figures, but they will serve 
to illustrate our purpose: 
| 3 g 
3 = a = 
gz 6S 8 a 86 
2 Cs B se 
So oS 8 6&2 =& 
‘9 a a & 3 Se 
au de fe gh Fe 
gE 2 £ & 
s s 4 g 5 
4 
a a 4 
RMAg Gecousuks 70 0to100 50to140 98  90t0 106 
DOR eesicutaas 60 70to140 70to140 101 95to110 
Monkey ...... 90 380to140 30to140 101 95to 108 
Horse ......... 80 20t0120 20t0120 99  95to105 
HOWL. a sinss dena 80 20t0140 20to140 107 100to115 
Newly hatched 
chick ....... 90 70to100 40to120 108 100to115 
Fertile egg at 
start of incu- 
bation ...... 103 =382to110 31t0125 103 31 to 125 
Egg incubated 
three days .. 103 98to105 80to118 103 95 to 118 
Egg incubated 
eighteen days 103 75to105 50to118 106 98 to 116 
This table shows, among other things, that we are consider- 
ing in the chick not a new proposition to which the laws of 
general animal life do not apply, but merely a young animal 
during the process of growth, to a point where its internal 
mechanism for heat control, has power to maintain the body 
temperature through a greater range of external temperature 
change. 
In the cooling process that occurs after laying the living 
cells of the egg become dormant, and like a hibernating ani- 
mal, the actual internal temperature can be subjected to a 
much greater range than when the animal is active. After 
incubation begins and cell activity returns, and especially 
after blood forms and circulation commences, the temperature 
of the chick becomes subject to about the same internal range 
as with other warm blooded animals. 
In the case of fully formed animals, the internal tempera- 
ture is regulated by a double process. If the external tempera- 
80 
