Forebrain and Midbrain of Lizards 
13 
Euspondyhis rahmi 
Gymnophthalmus speciosus 
Leposoma purietale 
Neusticurus ecpleopus 
Ophio gnomon dbendrothii 
Pholidoholus montium 
Prionodactylus argulus 
Proctoporus h olivia/mis 
Tupinambis nigropunctatus 
Gerrhosauridae 
GerrhosoMms validus 
Cordylidae CordyVus cordylus 
Platysaunis intermediiis 
Anguidae Anguis fragUis 
Anniella pulchra 
Gerrhmiotus midticarinatiis 
Ophisaurus compresstis 
0. ventraMs 
Xenosauridae Xenosaurus grandis 
Helodermatidae 
Heloderma horridum 
H. suspectum 
Varanidae Varanus bengalensis 
V. flavescens 
V. indicus 
V. niloticus 
Lanthanotidae Lanthanotuis bomeensis 
scribed in this study are genus- or family- 
specific and do not exhibit continuous varia- 
tion across taxonomic categories. 
Histochemistry 
Animals were killed by decapitation under 
sodium pentobarbital anesthesia (20 mg/kg). 
Following decapitation, the brains were dis- 
sected free and then placed in plastic embed- 
ding molds containing a commercially pre- 
pared, water-soluble resin. Quick-freeze was 
achieved by immersing the brains in 2- 
methyl-butane cooled to —70° C. Twenty-five 
micron transverse sections were then cut on 
a Harris cryostat at —20°. The sections were 
immediately attached to slides and dried for 
10 minutes in a vacuum-desiccator at room 
temperature. Two methods for demonstrat- 
ing enzymatic activities were used : The Koelle 
method (Gomori, 1952) for acetylcholin- 
esterase (AChE) ; and the method of Pearse 
(1960) for succinate dehydrogenase (SDH). 
Incubation periods ranged from 30 minutes 
to 2 hours at 30-42° C. An incubation period 
of 1 hour at 42° C was finally selected as 
optimal for both histochemical methods. As 
a control for the specificity of the cholines- 
terases demonstrated, additional sections 
were incubated in the reaction mixture with 
butyrylthiocholine rather than acetylthio- 
choline as the substrate. No nonspecific 
cholinesterases were demonstrated by this 
method. 
The regional distribution of enzymatic 
reactions and their relative activities were 
analyzed by projecting individual sections 
and tracing the outline of the sections and 
the boundaries of the reactive zones. The 
optical density or absorbance (O.D.) of these 
zones was then measured using a Photovolt 
photometer (Model 502M) coupled to a Leitz 
Ortholux II microscope. The relative O.D. of 
different zones restricted to a single brain 
section was determined by setting the 
photometer to read infinite density when no 
light fell on the photocell and to read zero 
density when light was transmitted to the 
photocell through an area of the brain sec- 
tion judged to be most free of an enzymatic 
reaction. All measurements were made with 
a white light source (12v 50W tungsten 
halogen lamp). O.D. values less than 0.15 
were not reported since these values fall 
within the range of background absorbance 
of the unstained tissue sections. The range 
of intensities of the histochemical reactions 
is reported in terms of O.D. values to avoid 
the more subjective terms of light, inter- 
mediate, or heavy staining reaction which 
have usually been reported in studies of this 
nature. 
Autoradiography 
Three specimens of Gekko gecko were 
processed for autoradiography following the 
injection of 50 /i,C of L-(4,5-^H) -proline, 20 
ix.C/)A, with a 5 jul Hamilton syringe and 26- 
gauge needle. The animals were allowed to 
