430 Combating Lousiness 
I omit from the foregoing table the records of the experiments by 
Kisskalt and Friedmann (1915, p. 397), Frankel (vi. 1915, p. 301), Hey- 
mann (hi. 1915, p. 253) and Zucker (1915, p. 294) who obviously exposed 
the insects to a high temperature for unnecessarily long periods. Kisskalt 
(n. 1915, p. 154) states that 70° C. kills nits but does not give the time of 
exposure. Wulker merely states that nits are “quickly” killed at 60° C. 
and that they appear to coagulate. None of the authors cited here and 
in the table record how they tested the thermal death-point of nits. 
My tests were carried out as follows: 50 fertile corporis eggs, laid on 
hair 24-48 hrs. before, were tied in bunches of 5 with silk thread. One 
end of the thread was weighted with a piece of wire whereby it was 
lowered vertically into a Nuttall microscope-thermostat through the 
centre of a glass tube attached by rubber bands to a thermometer. The 
nits were lowered to the level of the thermometer bulb which extended 
slightly below the bottom of the tube into the heated chamber. The 
eggs were examined microscopically after exposure and subsequently 
incubated at 30° C. with controls to see if they hatched. 
The foregoing records demonstrate that corporis nits are killed by 
dry heat at 65-70° C. in 1 minute, and at 55-61° C. in 10 minutes. 
( b ) Experiments with the active stages. 
Length of 
Result 
Temperature 
exposure in 
+ = killed 
Authority 
"C. 
minutes (') 
± =some killed 
(reference 
(dry heat) 
& seconds(") 
0 = survived 
see p. 435) 
72° 
y 
+ 2 (J 1 $ killed (Turned red in 1 hr at 30° C. 
Young adults fed ca. | hr before heating)... 
Nuttall 
71° 
V 
2 (J 1 $ ditto ... 
,, 
65° 
‘promptly” 
+ adults ... 
Widmann 
65° 
“ at once” 
+ unfed lice 
Zucker 
65° 
15' 
+ gorged lice 
99 
65° 
30' 
4- no particulars 
Kinloch 
59° 
25" 
± 2 $ fed, one killed, one recovered and lively 
after 24 hrs ... 
Nuttall 
57° 
45" 
+ 2 ? fed . 
99 
55° 
1-2' 
+ no particulars 
Wulker 
55-56° 
5' 
+ ,, „ 
Galli-Valerio 
50-56° 
15-20' 
+ ,, „ 
Heymann 
52° 
2'30" 
O 2 $ gorged, fell over as if dead in 2' 10" but 
lively after 24 hrs . 
Nuttall 
50-52° 
5-15' 
+ no particulars' 
Galli-Valerio 
50° 
10' 
,, ,, ... ... ... ... 
Wulker 
50° 
30' 
± -fe second stage larvae survived 
Bacot 
Or 
c 
o 
30-45' 
+ no particulars 
Noeller 
49° 
2' 
4- 2 $ unfed, one killed, one immobilized 24 hrs 
and died 
Nuttall 
O 
GO 
4' 
+ 2 $ unfed . 
99 
