PROJECT REPORT 
COMMITTEE ON FOOD RESEARCH 
QUARTERMASTER FOOD AND CONTAINER INSTITUTE 
FOR THE ARMED FORCES 
CHICAGO ILLINOIS 
IISKARCI AND BRANCH 
HILITAXT PLANNING DIVISION 
OPPICK OP TM 
QOAKTBIMA8TBK GKMXKAL 
TOm^S!UJ?FMWrvity 
LOCAL ft©st 168th St., New York, 3£,N.Y 
onn si otecnooi or PuciifTE&hlTh 
OEF-WnAGlt1'1-1 njgisnc 
OFFICIAL I NJIESJI SAJ0R4 ,, T. 
L. J. Golclwater, M.C. 
C0lLA.WT0fS 
E. Shils 
REPORT NO. ST 
FILE 
~fbR.Jp e&ii&q: mis'w l""NEyvtJintrBT' "TW? 
g 
INITIATION DATE 
Tl TL **£ J FR0§RE$S REFONT [ jPHASE NEFONT [ J ANNUAL REFORT [ ]TERMI NATION REPORT 
Physiology of Appetite 
SUMM ARY 
1. Most of the rats were able to maintain their weight or gain sligntly 
in a self-selection maintenance situation. 
2. The selections of most nutrients varied greatly from day to day and 
week to week within the same cage and also between the two groups of 
litter-mate-rats. Of special interest is the fact that in one cage average 
casein intake remained quite constant; in the other cage it fell off 
gradually but persistently. 
3. Bee.use of the marked variations it is concluded that self-selection 
maintenance is not a technique that lends itself to discerning small but 
significant changes in intakes unless very large numbers of rats are used. 
This would vary, however, depending on the nutrient, for the intakes of 
some substances were much more stable tnan others. 
4. "Positional eating” may occur with group feeding, contrary to the 
observation of Young (J. Comp. Psych. 5Y 371, 1944). while it is not a 
constant finding its occurrence makes random changes in the positions of 
tne solid foods necessary. 
5. The amount of intake of nutrients is apparently regulated largely 
by the volume of tne solution that the rat chooses to take end not by 
the concentration. Changes in concentration do not reflect themselves in 
similar changes in volume. With the possible exception of riboflavin the 
vitamin intake was far above physiological requirements. . 
P-1011 #2 
(Continued) 
1 
COMO FORM 
S April 46 
12-121 
(Kwiamd) SDLF-SEL. CTIdN EXPWRII HIT 
I* Description of Cages. 
The most serious problem in cage design for self-selection experi- 
ments is that of providing for accurate measurement of solid food intake. 
Rats have a habit of carrying food in their paws and in their mouths from 
the food cup to some part of the cage tdiere it drops through the fldor 
screening into the shavings, making accurate measurement of food intake 
impossible, 
A modification of an idea suggested to us by Dr, 2, C, Albritton of 
the Department of Physiology ©f George 'Washington University, Washington, 
D. C,, was tried and proved satisfactory. In his self-selection cages Dr. 
Albritton employs truncated, cone-shaped, inclined runways which are loca- 
ted inside the cage and at the bottom of which are food cups. This device 
forces the rat to back up when leaving the cup, and in so doing its front 
paws must be used for balance and motion, depriving the animal of the 
opportunity of carrying food. 
In our cages (Figure l), the runway is placed outside the cage for 
two reasons: (l) to reduce the food loss to a still greater extent, and 
(2) to eliminate the necessity of opening the cage whenever food cups 
have to be replaced. The runway was built of wire mesh in the shape of a 
truncated cone. The measurements, 2 3/V' at the top, 2" at the bottom over 
a length of 7% were chosen so as to allow young adult animals to crawl 
through the runway and yet to prevent then from turning around once there. 
Continued 
F-1011 #2 FIGURE 1: Representative Portion of Self-Selection Unit Showing Essential 
Elements.• 
Food Runway 
Flanged Collar 
Drinking Tubes 
Screw-cap 
Food Cup 
Removable Pan 
P-1011 
Continued On our cages the runways are placed in a vertical position rith 
the wider diameter at the top, forcing the rats to use their front legs 
for balance and notion and so preventing then from carrying food back 
into the cage. Food scattered or dropped is collected in a container sur- 
rounding the food runway to half its length, h'ith this device an accurate 
record of food intake can be kept. 
The runway is attached to the cage by means of a flanged collar and 
the food cup is secured to the runway by means of a screw-cap which is 
permanently fixed in its position by soldering it to the end of the runway. 
A rectangular cage, 25" x 15g" x 10 >n serves as the basis of the 
self-selection unit, the Mrat cafeteria”. The sides and top of the cage 
are of 18 gauge, l/V mesh sustained by an alum, nun alloy or sheet iron 
frame. The floor of the cage is two inches from the bottom of the frame 
and consists of a removable wire screen of IS gauge g" wire mesh. Beneath 
the floor, yet within the cage frame, is a galvanized metal pan, removable 
to facilitate waste disposal. 
The entire front of the ca e is hinged and serves as a door. Experi- 
ence with this type of door, however, indicates that its purpose would be 
better served by a smaller opening about 7" wide located in the center of 
the front side of the cage. This change in design was ordered for addi- 
tional cages now under construction. 
A metal strip 1" wide, attached to the rear of the. cage, serves as 
an anchorage for drinking tubes used in the self-selection. The calibra- 
ted drinking tubes used were of the conventional design. 
P-1011 #2 
Continued II* Height maintenance. 
The ability of the rats to maintain their health and weight in the 
"rat cafeteria" was investigated first. 
Twelve 120 day old female rats of the Sherman strain were used. These 
were distributed between two cages, three each of two litters in each cage. 
The purified nutrients offered were as follows: 
CaClo - 2/ solution Thiamine - (1) 200 mcg/nl 
(2) O0 ncg/ml 
KC1 - 1/ solution 
Riboflavin - (1) 25 ncg/ml 
HgSO - 0.5/ solution (2) 5>0 mcg/ml 
Tap Water Niacin - (1) 1000 ncg/ml 
(2) 100 ncg/ml 
Na HP0, - (1) ko 
(2) 6/ Pyridoxine - (l) 200 meg/ri 
(2) 100 mcg/ml 
NaCl — 3/° 
Ca Pantothenate - (l) 100 mcg/nl 
Biotin - (l) 5 mcg/ml 
(2) 0,1 mcg/ml 
Choline chloride - 3000 meg fa1 
Vitamin A (in corn oil) 100 I.U./ml 
Corn oil 
Casein, vitamin free - as a solid 
Cerelose - as a solid 
The nutrients in liquid form were offered in calibrated tubes of capa- 
cities best suited to the individual concentrations used. Because of the 
limited capacity of the food cups, two food runways were set up for each 
solid nutrient. 
’.'eights have been recorded at weelzly intervals for a five week period 
and are tabulated in Table I. 
Only eight of the twelve rats gained weight in this period, two main- 
tained their weight and two lost weight. The rats are being continued on 
self-selection. 
Continued 
P-1011 #2 J.ABLE 1: heights of Rats Before and During the Five Week Self-Selection 
Period. 
Cagd I 
'Rat 
! * 
Before 
Self- 
|Selection 
1st Leek! 
2nd Leek! 
3rd Week 
Uth Week 
5th Week 
; 
! Gins. 
Gms. 
Gms. 
Gms. 
' Gms. 
Gms. 
Litter 1 
l 
197 
205 
211 
206 
205 
197 
it 
2 
189 
198 
207 
210 
204 
207 
ii 
3 
200 
*.09 
219 
, / 
/4 
221 
2.15 
Litter 2 
4 
193 
204 
214 
216 
213 
213 
ti 
5 
177 
187 
188 
183 
176 
170 
ii 
6 
155 
165 
176 
? 
177 
176 
183 
Cagell 
Litter 2 
7 
182 
178 
19C 
182 
181 
179 
h 
8 
202 
212 
2*.0 
*24 
<.29 
223 
ii 
9 
171 
174 
185 
182 
185 
179 
Litter I 
10 
207 
217 
✓ci9 
210 
198 
t! 
11 
211 
230 
240 
237 
240 
243 
it 
12 
195 
*:03 
208 
200 
202 
216 
III -stake Variationi 
In the initial five week period during v.hicn tho rats were on self- 
selection main ten; nee, tne daily intakes of each of tne 17 nutrients 
\ 
offered (listed on page 4) were recordec. for eecn of the two groups. 
The extent of tne variations of each of tne nutr;.ents within each 
cage and between cages is presented in three different ways: 
(1) Expressing the range of intake of eacn nutrie. ft in each cage 
in terms of percentage variation from the minimum intake (Table 2). 
P-1011 -l2 
Continued (2) Charting the average d- ily intaxes of the nutrients on a weekly 
basis (Fig. 2). 
(3) Calculation of the standard deviations for each nutrient for 
each week (Table 3). 
Examination of these data shows marked variation of intake for most 
of the nutrients. Thus in terms of average percentage variation from tne 
minimum intake (Table 2) only NagHPO/., NaCr and cerelose nave a range 
below 100%, while KC1, vitamin A in corn oil, riboflavin, pyridoxine, 
corn oil and casein have ranges between 100% and ,.00%. The ranges of 
the remaining nutrients varied up to 61o% of the minimum intake,as in 
the case of biotin. 
TABLE 2; Range of Weekly Mean Intaxes of Nutrients; expressed as 
percentage variation from tne minimum intake. 
Nutrient 
Group I 
Group II 
Averagej 
Nutrient 
Group I 
Group II 
Average 
% 
Q 
% 
% 
% 
CaClp 
600 ' 
40 
3^0 
Riboflc vin** 
160 
110 
135 
KC1 
110 
445 
16& 
Niacin'0' 
475 
50 
460 
MgSC>4 
180 
6^0 
400 
pyridoxine'0" 
*-50 
85 
165 
H^O 
310 
400 
455 
| J3a Pan 
350 
345 
335 
N&2HPO4* 
60 
90 
75 
Choline 
00Q 
500 
390 
NaCI 
90 
80 
85 
Corn Oil 
80 
0 
0 
CM 
140 
Biotin** 
1500 
14.0 
310 
Cerelose 
14 
pc 
19.5 
Vit. A (in 
85 
145 
105 
Casein 
0 
0 
i-V 
45 
110 
corn oilj 
m, • • "X— 
Tina mine 
770 
300 
535 
A 
* Over a 4 week period at one concentration 
** Over a 3 week period at one concentration 
P-1011 $ 2 
Continued C_ 
I’O..]. 
Biotin 
A 
Niacin 
Ca P:int othenete- 
Pyridoxins 
B 
Tap Watop 
Casein 
CaCl;, 
WttK L"/ V' F. h O S 
FlorliNl; 2: i-.vcrage Daily Intake rer 6 Hats for Bach of 5 Weekly Periods: - 
subscripts following each nutrient refer to cage number. 
Arrows refe'r to- time oil,changes in text) as 
follows: 
Pibof.l&vin - from c,b mcg/'m.l to 50 mcg/ml. 
Thiamine - 200 " " " 50 " " 
' Niacin - " 1000 ” M M 100 " " 
Pyridoxine - 200 " " ” 100 " " 
Biotin - " 5 ” ” " 0.1 ” " 
NavfiP04 - " 4% to 6% 
Continued 
P-1011 #2 D 
L 
F 
Corn oil 
R'” 
Oerelose 
Choline chloride 
i%so4 
Vit. A (in corn oil) 
Riboflavin 
thiamine 
W J\ L '/ <MOOS 
FIOuRl h: Average Daily Intake Per 6 Rats for Lack of 5 Weekly Periods: 
subscripts following each nutrient refer to cage number. 
Arrows refer to time 0f change in concentration (see text) 
as follows: 
Riboflavin - from 15 mcg/ml to 50 mcg/mi 
thiamine - " 100 " ” ” 50 " " 
Niacin - " 1000” ” " 100 " ” 
Pyridoxine - 11 100 " ” ” 100 ” " 
Biotin - ” 5.0” ” ” 0.1” " . 
NagiiP04 ” 4p to op 
P-1011 1r2 
9 
Continued The differences between the two groups of rets in the intake of 
particular nutrients ere striking; in many instances these differences 
ere greeter then the variations between nutrients. 
Group I, for example, shows an average intake of MgS04 (Fig. IE) 
varying from 15 mis. to 45 mis. and back to 15 mis. over the five week 
period; group II shows an average intake (Fig. 2E) rising progressively 
from 2 mis. to 12 mis. over the same period. Niacin average intake (Fig. 2A) 
increased from 2 mis. to about 10 mis. after a reduction in concentration 
to one-tenth of the original concentration; the average niacin intake 
for group II (Fig. 2A) fell from 3 mis. to 2 mis. and then rose to 6 mis., 
with a similar reduction in concentration. Similar differences between the 
two groups of rats are evident in the a: se of mi ny of tne other nutrients 
as shown in Figures 2A-2F. 
The standard deviations (Table 3) of NaCl, shown in Table 2 
to be relatively stable in respect to intakes, are consistently less 
than one-half of their respective average daily intakes. The standard 
deviations for cerelose are even lower, being consistently less than 
one-cuarter of the means. 
Standard deviations for these three nutrients seem to show little 
variability. Standard deviations for the other nutrients varied con- 
siderably. For example, the standard deviations of biotin vary from 
50% of the mean to 20% greater than tne mean in group I; in group II 
from 50% of the mean to 100% greater tnan tne mean. Intake of thiamine 
shows standard, deviations which vary from 30% of the mean to 500% greater 
than the mean in group II; from 75% of the mean to 25%greater than tne 
P-1011 r;2 
Continued j 
.1 s' 
let 
yveek 
2nd 
week 
T 
3rd week 
4th 
**eek 
5tu 
week 
* Gage j/ 
I 
11 
1 
II 
1 
II 
T 
± 
11 
I 
II 
! 
! Wiatrients 
m 
sdj 
m 
sd 
m 
sd 
m 
sd 
m 
sa 
m 
sd 
m 
sd 
ra 
sd 
m 
sa 
a 
sd 
i Ob-Gxfj 
.46 
.14 
.21 
. 05 
.44 
.09 
•4 
.01 
.89 
.77 
.33 
% 
2.3 
2.0 
.31 
.27 
3.1 
S« j 
.43 
.28 
Uci 
‘0.6 
10.3 
6.8 
s 4 
26.0 
3*. 3 
9.2 
7,0 
36,3 
6.4 
12. J 
2.3 
20.6 
8.7 
14.7 1 
6v6 
16.3 
2.8 
28.3 
14.8 
1 
i i joGG/x 
15 .2 
8.8 
1.5 
.88 
21.4 
10.7 
5.5 
4.5 
4‘c. 7 
18.0 
7.3 
6.8 
53.1 
15.9 
8.7 
6^4 
16.4 
10.6 
10.9 
5.6 
! Tap 'water 
i 
2.3 
1.7 
11.4 
. , 
0.0 
5.8 
4.1 
12.7 
5.6 
4.9 
2.7 
21.9 
3.4 
9.1 
7.0 
11.1 
; 5.6 
9.6 
4.6 
7.1 
3.3 
; i»ayit>04 
I 
. ! 
60.b;23.6 
58.4 
0 7 
* 
28.0 
8.7 
40.3 
21.5 
32.1 
7.3 
24.9 
7.1 
30.3 
3.6 
20.9 
5.9 
44.4 
10.9 
26.2 
9.2 
1 
riaCl 
14.5 
'X 'X 
. 
11.8 
12.4 
5.3 
23.5 
8.1 
6.2 
1.7 
18.2 
4.7 
15.8 
s.o 
32.6 
9.8 
11.0 
5.4 
23.9 
6.6 
i i5iotin 
.2 
.1 
5.7 
4.3 
3.8 
3.8 
81.1 
8.8 
.97 
.95 
13.0 
7.7 
* 
.98 
1.0 
1.5 
2.9 
5.9 
5.0 
9. C 
4.3 
i 
1 Vit a(in 
5.9 
U . 1 
rj rj 
1 . / 
1.4 
2.9 
.18 
7.6 
. 28 
3.6 
.53 
7.8 
2.7 
3. 2 
.6 
4.0 
2.9 
5.9 
1.3 
. n 
*± . ( 
.65 
, corn oil) 
1 jt, . 
; in 1 am me 
3.9 
8.9 
•X rz 
• KJ 
2.3 
4.4 
4.9 
2.6 
14.3 
* 
.99 
.62 
2.8 
2.1 
.36 
.25 
2.5 
5.3 
3.2 
2.5 
10.: 
3.6 
I 
i Riboflavin 
71 
. 1 J. 
. 5 
. 46 
.46 
.41 
. 38 
.44 
.37 
* 
.34 
. 43 
.43 
.14 
.9 
.37 
.89 
.53 
.43 
.2 
.9 
.45 
1 
; iMiacin 
1.3 
1.1 
.9 
.51 
1.5 
1.8 
2.1 
1.5 
* 
1.4 
1.3 
b.5 
4. 6 
1.1 
2.3 
10.8 
3.6 
6.4 
7.0 
8.4 
6.5 
i 
1 Pyridoxine 
7.2 
4.5 
9.5 
4.1 
12.0 
6.5 
9.9 
2.5 
* 
h.i 
3.3 
8.6 
13.2 
.93 
.8 
12.7 
4.6 
3.1 
2.8 
6.9 
6.1 
| 
Ca Pan 
7.8 
2.9 
12.5 
2.8 
5.4 
1.9 
8.7 
6.3 
2.7 
2.8 
8.5 
c. 
• Ci> 
1.7 
1.4 
6.0 
7.0 
2.5 
1.4 
2.6 
2. 2 
; Choline 
5.7 
8.0 
5. 6 
2.4 
<"< rX 
8.9 
. 66 
1.2 
4.9 
2.3 
3.0 
3.1 
5.1 
5.1 
.8 
2.8 
1.5 
1.1 
3.4 
2.0 
i 
! Corn oil 
I 
d.3 
8.1 
7.8 
2.9 
3.5 
.85 
4.9 
1.7 
3.7 
1.2 
4.3 
.71 
4.0 
1.2 
2.4 
1.5 
3.8 
1.5 
• 
1.7 
Cerelose 
v ! 
28.6 
2.8 
85.1 
r> rr 
• O 
31.9 
7.8 
22.9 
6.0 
31.3 
4.5 
22.6 
3.3 
30.1 
■8.9' 
ch r\ 
60 • \J 
1.2 
32.7 
.0 
26 = 
5.4 
\ 
’ Casein 
17.5 
4.9 
15.8 
4.0 
15.8 
1.8 
14.9 
4.2 
11.0 
.6 
12.6 
2.0 
8.1 
J..5 
13. : 
8 
5.7 
.8 
12. 
8.7 
TABLE 3: Deviations Prom Mean Daily Intakes Per Cage For Each of 5 Weekly •. -j.’.ods. 
* Changes made in concentration from that of preceding weeks (see Pig. &). 
P-1011 
Continued me?, n in group I. 
Stc ndard deviations for KC1, vitamin A in corn oil, casein and corn oil 
? re generally 50% of their respective means or less (Table 3). Those 
for CaClp, water, riboflavin, niacin, calcium pantothenate, 
choline chloride and pyridoxine vary from approximately 50% of their 
respective means to values equal to or slightly greater than the means. 
IV Positional Eating: 
A study was made of the problem of "positional eating". The four food 
runways were numbered according to their position around tne cage 
as follows; 
Position 7fl - left front of cage 
Position ij3 - left rear " " 
Position #4 - right rear " " 
Position ,v 6 - right front " " 
The solid foods, c. sein end cerelose, were moved as indicated bexow 
and the intake and positions were recorded daily. In cage I tne 
positions of these foods were cnnnged daily in a random manner for 
a three wTeek period and then were kept constant for two weeks; in 
cage II the positions were changed daily for the entire five week period. 
Table 4A shows the percentage of total weekly intake of each of 
these t o foods at each position in cage II for tne five wreexly periods. 
It is apparent tnat the animals ate more of tne solid foods from 
position l. than from any of tne otners. Out of 19 possible choices, 
eating position 1 ranked first in intake if times and ranged second 6 times. 
This left only the one remaining choice to fit tne two remaining ranks, 
a condition whicn is well above the probability due to chance sampling. 
P-1OIL H2 
Continued . TaBLE 4A: Pe rcentage of Total Intake from Each Food Cup at Each Position. 
CAGE II 
Cup I-Cerelose 
Cuj- 
IV-Cere.lose 
week 
1st 
2nd 
3rd 
4th 
5th 
1st 
2nd 
3rd 
4 th 
5th 
i Positions 
% 
% 
°/o 
% 
% 
% 
% 
% 
% 
fe 
! 
1 
i 
4 2. 2 
nr. 
24.3 
26.0 
37.0 
36.8 
23.5 
37.4 
53.4 
r 
i 
1 00 
1 <.>* 
i 
3 
IS. 9 
21.5 
47.2 
20.9 
26.0 
21.2 
22.7 
29.0 
19.0 
23. 2 
4 
27.3 
co • 5 
28.5 
29.0 
24.0 
25.0 
20.0 
— 
26.0 
30.2 
6 
10.6 
21.5 
— 
24.1 
13.0 
17.0 
33.8 
33.7 
21.6 
18.1 
Cup XI- 
Casein 
Cup Ill-Casein 
Position 
% 
°/o 
7* 
% 
> 
ye 
> 
/e 
ye 
ye 
1 
24.8 
32.6 
— 
24.7 
23.4 
43.5 
45.8 
19.0 
34.6 
31.0 
3 
34.1 
29.0 
25.7 
22.5 
17.4 
82.2 
11.4 
37.5 
28.6 
27.1 
4 
23.3 
28.8 
52.0 
30.7 
30.8 
15.8 
26.2 
21.4 
23.1 
23.2 
6 
17.8 
9.6 
22.3 
22.1 
28.4 
18.5 
lo. C 
28.1 
14.7 
13.7 
TABLE 4B: Percentage of Total Intake from Each Food Cup at Each Position 
Cage i 
Cup I-Cert 
slose 
Cup IV_Cerelose 
Cup II-Caseir 
Cup 
Ill-Casein 
Week 
1st 
2nd 
3rd 
1st 
2nd 
3rd 
1st 
2nd 
3rd 
1st 
2nd 
3rd 
Positions 
* 
a/o 
% 
% 
% 
> 
% 
% 
% 
(ii 
/O 
% 
1 
£2.0 
30.6 
16.8 
21.0 
22.2 
21.1 
25.4 
14.4 
20.7 
25.5 
17.9 
2 2.0 
rz 
26.9 
27.0 
52.8 
25 • 3 
20.3 
«, n t? 
• ». ' 
19.9 
31.0 
17.9 
33.9 
36.1 
27.5 
4 
28.5 
23.6 
21.1 
24. 6 
15.1 
26.1 
23.9 
25.8 
11.5 
-- 
23.5 
18.3 
6 
22.6 
13.6 
19.4 
27.7 
32.4 
29.5 
30.3 
28.9 
39.9 
30.4 
22.4 
o r i 
<0*8.1 
P-1011 
Continued Tabme 4B presents a similar breakdown of the tnree weex period 
in which the positions were changed in cage I. In this case tne dis-. 
tribution of tne amount of food intake is much more in accordance 
with random choice. 
Thus, in tne behaviour of the rats in one cage, there appears to 
be a clear-cut example of "positional eating", while in the other 
cage this was not so apparent. 
V Changes in Concentration: 
The effect of changes in concentration on intake, both liquid 
and solid equivalent, was next investigated. Fith slight variations, 
concentrations of the liquid nutrients first employed were those used 
by Richter and Hawkes ( am. J. Physiol. 13i 639, 1943) ana are given 
on page 4 under weight maintenance. Sodium phospnate (dibasic), 
thiamine hydrochloride, riboflavin, niacin, pyridoxine and biotin 
were selected for change in concentration. The results of the changes 
are tabulated in Table 5* 
a. Effect on volume. 
Chen tne concentration of sodium phosphate was increased from 4% to 6% 
there was l decrease in liquid intake of 55% in cage I and a decrease 
in liquid intake in cage II of 4S%>. The concentration of thiamine 
was decreased to one-quarter of the original value (i.e. from 200mcg/ml 
to 50 mcg/ml). Following this the licuia intake decreased to nne- 
seventn of its previous value in cage I while in cage II it decreased 
to one-half of its previous value . Doubling the concentration of 
riboflavin from 45 mcg/ml to 50 mcg/ml was followed by a slight in- 
crease in intake in cage I and a tnree-fola increase in cage II. 
P-1011 -■?, 
Continued Tuble C; Influence 01 Cha.ngo in Concentre. t.i on on *re . il-.1- Intake per ;,n:i;ul 
i 
f' 
11 
i 
Inti ke 
In ta 
ke 
I'"it-:’ '-nU 
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P-1011 #2 
Continued then the concentration of niacin was reduced to one-tenth of its 
original value from 1000 mcg/ml to 100 mcg/ml the intake in cage I 
decreased 30%; in cage II, however, the reduction in concentration 
was followed by an increase in intake of 500%. When the concentration of 
pyridoxine was halved, from 100 mcg/ml to 100 mcg/ml, the intake 
of this vitamin was decreased by a proportionate amount in cage II 
while in cage I a reduction to one-tenth the original intake occurred. 
Reducing the concentration of biotin from 5 mcg/ml to 0.1 .mcg/ml 
v.as followed by an increase in intake of 100% in cage I and a decrease 
in intake of 150% in cage II. 
b. Effect on intake of nutrient. 
As the concentrations of thiamine, niacin, pyridoxine and biotin 
were decreased, the intakes of the nutrients decreased in all instances, 
but the percentage of decrease varied greatly and the pattern of intake 
in the two cages was entirely different. As the concentration of 
riboflavin was increased the nutrient intake increased slightly in 
one cage ana markedly in the other. However, as the concentration of 
was increased, nutrient intaxe decreased in both cages. 
VI Conclusions: 
1. Most of the rats were able to maintain their weight or gain 
slightly in a self-selection maintenance situation. 
1. The selections of most nutrients varied greatly from day to 
day and week to eek within the same cage and also between the two groups 
of litter-mate rats. Of special interest is trie fact that in one cage 
average casein intake, remained quite constant; in the other cage it 
fell off gradually but persistently. •. . ... ,.ro 
P-1011 42 
16 
Continued 3. Because of the marked variations it is concluded that self- 
selection maintenance is not a technic ue that lends itself to discern- 
ing small but significant changes in intaxes unless very large numbers 
of rats are used. This would vary, however, depending on the nutrient, 
for the intakes of some substances \.ere much more stable than others. 
4. "Positional eating" may occur with group feeding, contrary to 
the observetion of Young, * . While it is not a constant finding 
its occurrence makes random changes in the positions of the solid foods 
necessary. 
5. The amount of intake of nutrients is apparently regulated largely 
by the volume of the solution that the rat chooses to take and not 
by the concentration. Changes in concentration do not reflect themselves 
in similar changes in volume. Pith the possible exception of riboflavin 
the vitamin intake was far above physiological requirements. 
Young,P.T. - J. Comp. Psych. 37 371, 1944 
P-1011 #2 
Continued TASTE THREbnOLB LAPiA-ilMEHl 
Richter (Harvey Lectures 38 63,194k-3) studied the intake by rats 
of solutions of various toxic substances offered in gradually increas- 
ing concentrations in a simple choice situation with water as tne alter-,, 
native. It was thought worthwhile to repeat and extend some of his 
experiments. 
Mercuric chloride was the first substance studied. Tnree male rats 
approximately llo days old, of the Sherman strain, were used, each 
in a separate cage. 
Before offering the mercuric chloride an a ttempt was made to 
eaualize the vater intake from eacn of tne t* o tubes in order to rule 
out the effects of "positional " selection or other idiosyncracies. 
Tube positions were changed in a random manner. At the end of eight 
days total intakes were as follows: 
Tube jfl 
Tube ftU 
Rat #1 
204 nils. 
216 mis 
Ro t #2 
238 " 
177 " 
Rat #3 
332 " 
220 " 
Except in the case of Ret #1, equalization did not taxe place. 
Mercuric chloride was therefore introduced into that tube showing tne 
greatest intake so that any decrease would be more readily detected. 
In the next 10 days each of tne tnree rats were given mercuric chloride 
solutions of regularly increasing concentrations. Each concentration 
of mercuric chloride was offered for' a two-day period followed by water 
as a check after every two succeeding concentretion revels. Tubes were 
changed in a random manner. 
P-1011 
Continued FIG-UitL 3: Affect of Increasing Concentration of HgClc on Intake 
Dash. Line Water 
Solid Line _HgCl<. 
Y LO \ O I N T A \\ C. 
In 
S nv> t 1IV 
Qp'i'o 
Ptf '.Cot H o C U 
The concentration of tne solution was increased from 0.0001% to 
0.004% when intake of mercuric chloride stopped. At this point water 
was substituted for the mercuric chloride. 
Figure 3 sho> s the intakes of mercuric chloride solutions and of 
water as tne eoncentm tion of the former was increased. 
It can be seen that the intake of mercuric chloride decreased 
sh roly as the concentrations increased beyond 0.001%. At tnis point 
there is an immediate increase in water intake showing the response 
to a substitution of water for mercuric chloride. 
These results closely follow those reported by hienter. 
In a similar manner the taste threshold for sodium arsenite was 
investigated(Figure 4)• As tne concentration of sodium arsenite 
was increased from 0.0001% to 0.01l%, intake decreased from 30 mis. 
P-1011 jL2 
Continued FIGURE 4: Effect of Increasing Concentration of sodium Arsenite on Intake 
Dash Line Later 
Solid Line Sodium Arsenite 
(“LuiO ImT 
im 
Tih e 
Ptr Ctnt Csim. cF Sdi um G.'’ Se'rn t e. 
to about zero. Later intake over trie same period increased from DO mis. 
to 60 mis. 
then water was substituted for the sodium arsenite, on the Lind day, 
intake from this tube increased to i5 mis. The intake from the original 
. water tube decreased proportionately at tne same time. 
In general tne pattern for sodium arsenite follows that of 
mercuric chloride quite closely. 
P-1011 #2 
20