of 2 ,tg acetylcholine (ACh) was tested. No sweat response was detected in

19 Pages·2005·2.82 MB·English

J. Physiol. (1969), 203,pp. 13-29 13
With 2plate and 6text-ftgurem
Printedin GreatBritain
THE RESPONSE
OF THE SWEAT GLANDS OF THE NEW-BORN BABY TO
THERMAL STIMULI AND TO INTRADERMAL
ACETYLCHOLINE
BY K. G. FOSTER, E. N. HEY AND G. KATZ
From the M.R.C. Environmental Physiology Research Unit, London School
ofHygieneandTropicalMedicine, London, W.C. 1,andtheM.R.C. Research
Group on Respiration and Energy Metabolism in the Newborn, The London
Hospital Medical College, London, E.1
(Received 28 October 1968)
SUMMARY
1. Measurements of evaporative sweat loss were made on fifty-six
premature and full-term babies 1-67 days after birth with an infra-red
analyzer and a ventilated capsule placed onthe thigh. Measurements were
also made of total evaporative water loss while in a closed metabolic
chamber and of the regional distribution of sweating with starch-iodine
paper.
2. No sweating to thermal stimuli could be detected in infants of less
than 210 days post-conceptual age, even when rectal temperature rose as
high as 37.8° C. In older infants sweat was detected first on the forehead
andtemple, lateronthechest,andusuallyby240-260dayspost-conceptual
age on the legs (term 268 days). Generalized sweating on the limbs
appeared at an earlier post-conceptual age in the more prematurely born
infants.
3. The response ofsweatglands onthethigh to anintradermal injection
of2,tg acetylcholine (ACh) was tested. No sweat response was detected in
infants under 225 days post-conceptual age, while all infants born within
2 weeks of term responded. The response was often augmented after
2-5 tests at 5-10 min intervals; all the eight infants born within 2 weeks
of term who were examined twice in the first 2 weeks of life showed a
greater response on the second occasion.
4. An average of 414 active sweat glands/cm2 were detected on the
thigh in eight babies 7-10 days old born within 2 weeks ofterm. This was
61 timesthenumberfoundinadults. Themeanpeaksweatratetochemical
stimulation was however only 2 4nl./gland.min, which was 3 times lower
than the maximum rate recorded in adults.
14 K. G. FOSTER, E. N. HEY AND G. KATZ
5. In five infants with congenital defects of the brain and complete
absence oftemperature control there was no sweat response to thermal or
direct chemical stimulation ofthe glands.
6. Functional maturation appears to depend on intact central innerva-
tion and is marginallyhastened by post-natal factors. Immaturity ofthe
sweat glands can account for the lack ofany response to thermal stimuli
in premature babies, but not for themodest thermal responseobtainedin
babiesatterm.
INTRODUCTION
Recent studies have shown that in the new-born human infant total
evaporative waterlossincreases to onlyalimited extent at ahighenviron-
mentaltemperature, evenwhenrectaltemperaturerises ashighas 37.80 C.
This limitation is even more marked in infants born more than 3 weeks
before term (Hey & Katz, 1969). These findingsreinforcethegeneralbelief
that thermal sweating is limited inthe human baby at birth, and that the
severelypremature infant isunableto sweatat all. Wehavenowextended
this workbymeasuringwaterloss from the skin directlywith aventilated
capsule, and determined the effect of post-conceptual age on the ability
ofthe sweat glands to respond to both thermal and chemical stimulation.
A preliminary report ofsome ofthis work has been given (Foster, Hey &
Katz, 1968).
METHODS
A total offifty-six unrestrained and unsedated healthy babies ofknown gestation were
studied with the consent of their parents after delivery in the maternity wards of The
LondonHospital.Theparentsofnearlyone-thirdoftheinfantsstudiedwereinthemedical
or nursingprofession. Each infant's post-natal age was calculated from the time anddate
ofdelivery, while post-conceptual age was takenas originating 14 days afterthe first day
ofthe mother's last menstrual period. This date was confirmed by sequential neurological
examination ofthe infants after delivery usingthe methods employedin aprevious study
of total evaporative water loss (Hey & Katz, 1969), and by detailed assessment of the
physicalappearance(Farr,Mitchell,Neligan&Parkin, 1966).Alltheinfantswereofnormal
weight forgestation.
The nakedinfants were studied in an incubator at various environmental temperatures
while rectal temperature was monitored continuously with a thermistor. The pattern of
regionalsweatingwasstudiedwithstarchpaperpreviouslyimpregnatedwithiodinevapour;
thepaperwasnormallyapplied totheskinfor 30sec. Rectaltemperature wasnotallowed
above 37-80 C (1000 F). A small Perspex capsule 1 cmin diameterwas secured to the skin
onthelateralaspectofthethighinordertostudythesweatresponseofthisareatothermal
stimuli in more detail. (This site is often employed when obtainingsweatbypilocarpine
iontophoresisfordiagnosticpurposesintheneonate.Itwaschosenforthepresentinvestiga-
tion because it offered an adequate flat area, even in premature babies, from which the
capsulewasunlikelytobedislodgedbyspontaneousmovement.)Thecapsulewasventilated
with dry nitrogen, and this gas together with any evaporated sweat then passed through
SWEAT RESPONSES OF THE NEW-BORN BABY 15
acalibrated infra-redgas analyserand flowmeter at 0-1-0-3 1./mintomeasure therateand
volume ofsecretion (Foster, 1966).
The response ofthe sweat glands under the capsule to chemical stimulation was studied
by administering 2Bag acetylcholine in 0-2ml. saline at room temperature intradermally
through aneedle into the skin under the capsule (Foster & Weiner, 1967) with full aseptic
precautions. Therewasnoresponsetocontrolinjectionsofsaline(Text-fig. 1b).Thepresence
ofthe capsule and needle didnot appearto upset the child, though the actual injection of
ACh occasionally caused the child towake and cry for afew seconds. The insertion ofthe
needle caused momentary discomfort, but the procedure adopted seemed to cause less
disturbance than iontophoresis ofdrugs into the skin. Care was taken to keep the site of
injection as superficial aspossible inorder to elicit themaximumresponse; whencorrectly
placed, each injection caused a transient circular white mark on the surface ofthe skin.
Themaximumresponsewasassessedwhilethebabylayinawarmenvironmentof33-35°C
witharectaltemperatureofbetween37-3and37.60C.Countsofthenumberofsweatglands
activated by maximal stimulation with 2/sg AChwere made oneight ofthe infants using
the method ofThomson & Sutarman (1953).
A group ofeight healthy men and women were also studied for comparative purposes.
Thesubjectssat, dressedintheirnormalclothes,inaroomat24-25'C. Theresponsetoan
intradermal injection ofAChwasmeasured atnormal bodytemperatureusinganidentical
technique.
Estimates of the infants' total evaporative water loss and heat production at various
environmental temperatures werealso obtained atleast once onallbutnine ofthe babies,
usingthemethoddescribedbyHey&Katz(1969).Directmeasurementsofheatflowthrough
theskinweremadeintwenty-seveninfantswithaheat-flowdisk(Hatfield& Wilkins, 1950)
on the back ofthe hand, while the whole arm was surrounded by a thermostated water-
jacket maintainedat aconstanttemperature.
Five other infants with gross congenital abnormalitieswere seenafter admission to the
hospital for observation. The parents of these babies also gave their consent to all the
experimental proceduresundertaken. Theabilityoftheseinfantstocontrolbodytempera-
turewasstudiedcomprehensively, buttheywereonlyexposedtoarangeofenvironmental
temperature similarto thatwhichtheycouldexpectto experienceinahospitalnurseryor
athome. Infour ofthefiveinfants Quinizarinpowder (Guttman, 1937, 1940) was used to
detectathermalsweatresponse.Theresponsetopilocarpineiontophoresis(Gibson& Cooke,
1959) wastestedinall fiveinfants. Twoinfantswithlumbarmeningomyelocoelewerealso
studied.
RESULTS
The thermal response
No sweating could be detected in healthy infants ofless than 210 days
post-conceptual age (term 268 days) in an environment of 36-37' C,
even when rectal temperature rose as high as 37.8° C. Tests with starch-
iodine paper and Quinizarin powder were all negative, andnorise in total
evaporative water loss occurred. Direct measurement ofheatflow showed,
however, thattheinfantswereableto controlheatlossfromthehandeven
at this early age (presumably by changing skin blood flow). The infants
were also capable ofincreasing their heatproduction in cool surroundings.
A significant rise in total evaporative water loss always occurred in
infants of more than 220 days post-conceptual age tested at comparable
temperatures, and sweating could always be detected onthe forehead, the
16 K. G. FOSTER, E. N. HEY AND G. KATZ
anterior part ofthe scalp and the temples. Aprogressive increase occurred
in the number of areas where sweat could be detected in infants of over
230 days post-conceptual age, and there appeared to be an increase in the
magnitude of the response in the areas tested. A response was usually
detected on the shoulders and chest before it was found on the limbs. In
the majority of infants born within 2 weeks of term sweating could be
detected over most ofthe exposed areas ofthe body 4-14 days afterbirth.
0-3 Sweatsecretion(al./min) (a)
02( 2Pg
ACh s Restless Sleeping Crying Coolair
Sweatsecretion (al./min) 0 4 8 (b)
0-06 = = s Ui
0-03 U UU U U
Xo DoboU0 b
Text-fig. 1. Records oftherateandvolumeofsweatsecretionbeneathaventilated
capsule 1 cmindiameterplacedonthelateralaspectofthethighoftwonew-born
babies.
(a) The response on the ninth dayafter birth ofa 3-7kg infant born 2weeks
beyondterm.Thereisalargeresponseto2jugintradermalAChin02ml.saline.An
abnormally large thermal response appeared when rectal temperature exceeded
37.-3 C;thisirregularresponsewasaugmentedwhenthebabywokeandcriedbriefly
butceased promptlywhencool airwas blown overthe whole body.
(b) Theresponseontheeighthdayafterbirthofa2-7kgSinghaleseinfantborn
1weekbeyondterm.Therewasnothermalresponseevenwhenrectaltemperature
exceeded37.8 C(aresponsewaspresent1weeklater).Therewasnoresponsetothe
firsttwointradermalinjectionsofAChandanincreasingresponsetothreefurther
injections. Therewasnoresponsetoanequalvolumeofsaline (thesmallresponse
seen after the first ofthe two saline injections is assumed to be due to the small
amount ofAChleftinthelumen oftheindwelling needle).
Sweat always appeared most profuse on the forehead; it was often de-
tectedtherewhentherectaltemperaturewas only a little above 370 C and
before sweat was evident anywhere else on the body.
A particular analysis was made of the sweat response on the lateral
aspect ofthe thigh: there was good general agreement between the results
obtained with starch-iodine paper and the results obtained with the
ventilatedcapsule. Mostinfants bornwithin 2 weeks ofterm sweatedhere.
Occasionally therewas a latent periodduringwhich temperature was high
but apparently constant before the thermal response appeared. The
response obtained on the thigh was characteristically irregular; it was
often initiated or augmented when the child became restless or cried
SWEAT RESPONSES OF THE NEW-BORN BABY 17
(Text-fig. 1a), but sweating appeared to cease abruptly when cool air was
blown over the body. Most, but not all, infants of more than 260 days
post-conceptualagesweatedslightlyonthethighbeforerectaltemperature
rose to 37.80 C. In infants born several weeks before term, the response
appeared on the thigh at an earlier post-conceptual age; these infants
when tested more than 2 weeks after birth began to sweat about 240 days
after conception (Text-fig. 2). It seems clear that the onset of a thermal
responseonthethighisrelatedtobothpost-conceptualandpost-natalage;
tests with starch-iodine paper suggested that other areas ofskin behaved
in a similar way.
The highest rate of secretion at a rectal temperature of 37.6-37.8° C
varied with post-conceptual age in the manner outlined in Text-fig. 3a;
0
Lessthan 2weeks 00 o 0000@o°@o0--
after birth 0 000 00000000
More than 2weeks o 00 Oreo** ...
after birth 00000 0
Term
I
Post-conceptual I I I I I I I
age (days) 180 220 260 300
Text-fig. 2. The thermal response on the thigh under the ventilated capsule in
infants of differing post-conceptual and post-natal age. Rectal temperature was
37 80 Cexceptinafewinfantswhosweatedprofuselyatalowerrectaltemperature.
*,Secretionofsweattothermalstimulidefinitelyrecorded; 0,not observedatthe
highesttemperatureemployed.AX2testonthetwenty-threeresults obtainedfrom
babies between 239 and 259 days after conception indicated that the onset ofa
thermal response was related to post-natal age as well as post-conceptual age
(P = 005).
the peak rate recorded in fifteen infants 1-14 days old born within 2
weeks of term was 0-109+0-031 ,il./cm2.min (mean +S.E.). Such rates
of secretion were, however, usually only detected while the child was
crying and active, and were seldom maintained for more than a few
minutes; little sweating was observed on the thigh at this temperature
when the infants were quiet, in contrast to the fairly copious sweat
response detected on the head, and, on occasion, the trunk. The sweat
rates in Text-fig. 3a maybe comparedwitha calculatedestimate forbasal
transepidermal water loss of a little over 0-01 /td./cm2.min under most
conditions oflow airmovement andnormalhumidity (Hey & Katz, 1969).
Response to acetylcholine
The response ofthe skin on the thigh ofeach baby was also tested to an
intradermal injection of 2 ,ag ACh in 0-2 ml. saline. This strength ofdrug
was selected because studies had shown that although secretion was pro-
18 K. C. FOSTER, E. N. HEY AND G. KATZ
longed by a larger dose in adults, the rate of secretion recorded under a
capsule 1 cm in diameter only increased by an average of 7-5 % after
injection of 20jtgACh (Table 1). Tests on seven babies failed to demon-
strate a significantly greater maximum rate of secretion after the intra-
dermal injection of 20 instead of 2/tg ACh in the same volume ofsaline
(Table 1).
Noresponse to ACh was detected on the thigh ofinfants under 225 days
post-conceptualage,whiletheresponseofinfantsbetween225and250days
old was variable (Table 2). However, all infants born within two weeks of
term (between 254 and 282 days after conception) and tested within
TABLE 1. Themaximumsweatrateinadultsandbabiesrecordedwithaventilatedcapsule
1 cm in diameter after an intradermal injection of 2 or 20Itg ACh in 0-2ml. saline. Mean
results (+±S.E. ofmean)
Full-term Healthy
babies 3-10 adults 18-36
days old years old
Number ofsubjects ... 7 7
Response to 2/tg ACh (,ul./min) 0-214+0-078 0-377+0-058
Response to 20jug ACh (/zl./min) 0-238+0-083 0-405+0-061
Mean paired difference in 0-024+0-011 0028+0-011
maximum sweatrate
Significance ofthis difference P 007 P < 0-05
14 days ofbirth responded to this stimulus, though the maximum rate of
secretion variedgreatly (Text-fig. 3b). In many ofthe infants theresponse
to the first injection was small but an augmented response was obtained
after 2-5 tests were performed at 5-10 min intervals (Text-fig. lb). No
sex differences were detected. Ineight mature infantsthe response to ACh
was tested twice in the first 14 days after birth when rectal temperature
was 37 437 6° C. In each case the response was greater on the second
occasion (Text-fig. 4) andin five ofthe infants the increase was significant
at the 5% level. Sweat-gland counts were made in four ofthe infants: the
increase in response with post-natal age could not be accounted for by
changes in the number ofactivated glands.
Infourteeninfantsbornwithin 2weeks oftermthetestwasundertaken
inthe first 2 weeks afterbirth both atnormalbodytemperature, whenthe
child was vasoconstricted, and at high temperature on the same occasion
while vasodilated. The order ofthe tests was random; in the majority of
the experiments heat flow through the hand was measured continuously
during the study. The secretary response was slightly greater at high
rectal temperature in ten of the fourteen studies (paired variate test:
P < 0-01); the mean difference was 0-04/Ll./min.
There was a clear correlation between the highest rate of secretion
recordedunderthecapsuleinresponsetothermalstimuliandthemaximum
rate achieved in response to 2 fig ACh. However, the response to ACh
SWEAT RESPONSES OF THE NEW-BORN BABY 19
always exceeded the response to thermal stimuli with rectal temperature
between 37X6 and 37.80 C. Sixteen infants who responded slightly to 2,ag
AChdidnotrespondtothehighestthermalstimulus applied; the converse
never occurred.
0*
04 0.3r
* W
4D0_ a-
a _
'- 0-3 * m2 00*00
- 2 * 0
0
00W
02
00 0
(a) 00 0-1I. (b) 0 .0..0
-I1C1Rs. WW0k.0*-10 oL0...l..i-2 m2o0 a 0*000~0~~~~~~~g1~~.+~o~~ 0 0 00%0&*00 0:00o
200 250 !trm 300 200 250 t 300
T Term
Post-conceptual age (days)
Text-fig. 3. The relation between post-conceptual age and the maximum rate of
sweat secretionbeneath aventilated capsule on the lateral aspect ofthe thigh.
(a) Maximumresponsetothermalstimuliinpul./cm2.minatarectaltemperature
of37.6-37-8° C in full-term and premature infants 1-14 days old. Responses this
largewereonlytransientlyrecorded. Theenvironmentaltemperaturewasbetween
360 and 370C.
(b) Maximumresponsetoanintradermalinjectionof2jigAChin02ml. saline.
Sincethereisevidencethatthisstimulusactivatedtheglandsinonlyasmalland
variableareaofskinunderthecapsuletheresponsehasbeenexpressedasgl./min.
The conditions were as defined in Table 2. *, Full-term and premature infants
0-14 days old; 0, premature infants 15-67 days old.
TABLE2.Themaximumsweatresponserecordedafteranintradermal injectionof2jugACh
in 0-2ml. saline into the lateral aspect ofthe thigh in premature and full-term new-born
babies. The tests were undertaken in a warm environment of 33-35°C when the rectal
temperature was between 37.30 and 37-6°C. Meanresults (±s.E. ofmean)
Subjects Total sweat Duration of Maximum
volume response sweatrate
Group Number (Ud.) (min) (Pl./min)
Babiesborn43-70 6 0 0 0
daysbefore termand
1-14 days old
Babiesborn 14-42 12 0-076+0-029 36+0-8 0-026+0-012
daysbefore termand
1-14 days old
Babies bornwithin 13 0-263+0-087 4-9+0-4 0090+0-025
14 days ofterm when
12-72 hours old
Babies bornwithin 20 0-491+0-072 6-6+0-4 0-158+0-021
14days oftermwhen
4-14 days old
20 K. C. FOSTER, E. N. HEY AND a. KATZ
The response to intradermal AChininfants bornwithin 2 weeksofterm
wasalso comparedwiththeresponseobtainedinyoungadults. Thevolume
ofsweat secreted was very much greater in the adults, the sweat response
persisted for very much longer, and the maximum rate ofsecretion under
the capsule was almost always higher (Text-fig. 5). The mean differences
were significant at the 0.1% level (Table 3), but this could have resulted
from a difference in the way the injected drug spread or was inactivated,
003
c 02
0
9 0-1
0
0
0 5 10 is
Post-natal age (days)
Text-fig. 4. The effect ofpost-natal age on the maximum rate ofsweat secretion
after an injection of2Iug ACh in 0-2ml. saline. Results obtainedin eightinfants
bornwithin 2weeksoftermwhowere studiedtwiceundercomparable conditions
in the first 2 weeks after birth. The vertical bars indicate the s.E. ofthe means
(0) wheren 3 4.
rather than a difference in the responsiveness of the glands. The brief
response in the baby was certainly not the result ofglandular exhaustion
because the response to a further immediate injection was normal (Text-
fig. 1b). The number ofactive sweat glandsunder the capsule was counted
afterthe injection of2lagACh ineightbabies andeightadults. Therewere
61 times asmany active glands in the babiesper unit surface area, butthe
glands were activated over a wider area ofskin in the adults (Plates 1, 2).
Infants with developmental defects ofthe c.N.s.
Five mature infants were seen who had severe congenital defects ofthe
brain: one infant was anencephalic, one had severe hydranencephaly, and
three had large occipital encephalocoeles and microcephaly. The infants
neither shivered, became active, norincreasedtheirheatproductionabove
basal when exposed to a cool environment; no change in the thermal con-
ductivity ofthe skinoccurredinresponseto changes inenvironmental and
body temperature. It is likely that these observed defects oftemperature
.<. 1 ~~~~~~~~~~~~~Min.
SWEAT RESPONSES OF THE NEW-BORN BABY 21
control were caused by some derangement of the brain mechanisms in-
volved in temperature regulation.
The five infants failed to sweat anywhere on the body in response to
thermal stimuli, and the total evaporative water loss neverrose above the
normal basal leveleven athighenvironmental andbodytemperature. The
E 0-6
-7 . 2#egACh0 4 8
o 0-4
0
0-2
u
02.
U,
Text-fig.5.Recordsoftherateandvolume ofsweat secretion beneathaventilated
capsule on the lateral aspect of the thigh, showing the typical response to the
intradermalinjection of2jugAChin0-2ml. salineinanadult (-)andinanormal
8-day-oldinfant (......). Thenumberofglandsactivatedunderthecapsuleinthese
two subjects byinjection ofACh isrecordedinPlates 1 and 2.
TABLE 3. Comparison of the sweat response to an intradermal injection of 2Iug ACh in
adults and in new-born babies. The records were obtained from the lateral aspect ofthe
thigh usingaventilated capsule 1cm indiameter. Mean results ( s.E. ofmean)
Full-term Healthy
babies 7-10 adults 17-34
days old yearsold
Number ofsubjects ... 8 8
Total sweatvolume (1A.) 0-52+0-10 3-66+0-34
Duration ofresponse (min) 6-2 +0-4 19-1 +1-3
Maximum sweatrate (gl./min) 0-17+0-03 0-35+0-03
Estimatednumber ofactive sweat 414+49 64+6
glands per cm2
Estimated number ofglands 98+25 48+4
activated under the capsule by
injection of2/esgACHin 0-2ml.
saline
Maximum sweatrate per activated 2-40+0-57 7-51+0-63
sweatgland (nl./min)
infantsalso failed to secreteanysweatWhen testedwith pilocarpine onthe
thighonatleasttwooccasions. Boththechildrenwhoweretestedalsofailed
to respond to injections of 2, 20 or 200,ug ACh in 0-2 ml. saline into the
skin of the thigh under a ventilated capsule. The four youngest children
have since died. No abnormalities were found in the sympathetic nervous
system, the skin, or the sweat glands at autopsy.
Two other full-term infants were seen who had lumbar meningo-
myelocoeles and a complete flaccidparalysisofthelegs.Whereasthesweat
glands on the arm responded to both thermal and chemical stimulation,
those on the leg responded to neither.
22 K. G. FOSTER, E. N. HEY AND G. KATZ
DISCUSSION
Sweat responses at birth
Uchino (1939a, b) failed to detect sweating on the chest to thermal
stimuli onthe first day oflife,butsweatingwasrecordedbythe fourteenth
day after birth in twenty-seven out offifty-seven full-term infants. None
of the five premature infants born 3-6 weeks before term sweated until
at least 13 days after birth. Bruck (1961), however, reported that in nine
full-term infants studied on the first day of life 'beads of sweat appeared
on the forehead at rectal temperatures between 37X5 and 37.90 C; in three
cases sweat was also observed on the arms, legs and trunk'. Adamsons,
Gandy & James reported similar observations in 1965. Again, all the
infants born within 3 weeks ofterm studied by Hey & Katz (1969) on the
day ofbirth were able to more than double their total evaporative water
loss when rectal temperature rose above 37.50 C.
It has been thought that these reports conflict with those of Uchino,
butthefindingsare notnecessarilyinconsistent. Theobservationsreported
here indicate that sweating nearly always occurs first and most profusely
on the head, and only later on the trunk and limbs to any significant
extent. In several ofthe infants studied here and born within 2 weeks of
term no sweat was detected on the chest or limbs using starch-iodine
paper, and none recorded under the capsule on the thigh, until the infant
was several days old, although the rectal temperature was taken as high
as 37.80 C. In other infants generalized sweating was seen on the day of
birth, but only when rectal temperature rose above 37.5° C; in many of
Uchino'sstudies rectal temperature neverrose above thisvalue during the
first few days. We may conclude that all full-term babies were capable of
sweating on the day ofbirth, but that thermalsweatingwasmoregeneral-
ized and occurred at a lower body temperature in infants a few days old.
The sweat response to thermal stimuli ofbabies bornmore than 3 weeks
before term was small, and largely limited to the head. The change in
response to thermal and chemical stimulation summarized in Text-fig. 3
closely parallels the increase in total evaporative water loss at high
environmental temperature with increasing post-conceptual age (Hey &
Katz, 1969, Fig. 10). Seven infants capable ofsweating ontheheadwhen
hot did not respond to intradermal ACh on the thigh, but this appears to
be related to the fact that babies sweat on the head to thermal stimuli
at an earlier post-conceptual age than elsewhere onthe body. Every baby
that sweated on the thigh to thermal stimuli also responded at the same
site toACh. That the converse didnothold suggests that 2 ,tg intradermal
AChwasamoreeffective stimulusthanthehighesttemperatureemployed.
Uchino (1939a, b) found a clear and persistent sweat response in full-