Head 
2.17 ZYGOMATIC GLAND 
The zygomatic gland {gl. zygomatica) (some- 
times called the external orbital gland), (Fig. 2-58) 
is an oval-shaped gland which lies rostral to the 
parotid gland on the lateral surface of the masseter 
and temporalis muscles, completely outside the 
orbital cavity. It is yellowish-brown to brown in 
color (Figs. 2-61, 2-62) and measures 8-10 mm in 
length, 6.3-7.5 mm in breadth and 2.5-2.8 mm in 
thickness, depending on sex and season (Tables 22, 
22a). The dorsal portion is located immediately 
under the epidermis while the ventral portion is 
covered by the cheek pouch. It is applied to the 
lateral aspect of the masseter muscle and the ventral 
aspect of the temporal muscle. It overlaps the pa- 
rotid duct as well as the buccal nerve and, macro- 
scopically, presents an indistinct lobular structure. 
The secretory ducts of the zygomatic gland join 
intraglandularly and form the main duct, which 
leaves the dorsorostral fourth of the gland. 
The zygomatic gland has a tubuloalveolar structure and is of the 
serous type. The columnar cells which line the glandular acini do not 
contain fat droplets. The cytoplasm of the cells is finely granulated and 
the nuclei spherical and basally situated. 
In contrast to the parotid gland, which is con- 
tinuous with the surrounding tissues, the zygomatic 
gland is easily ablated. It is firmly attached only at 
the excretory ducts rostrally and afferent blood 
vessels caudally. 
2.18 NEUROCRANIUM AND BRAIN 
The brain (encephalon) is overlaid dorsally by 
paired frontals {os frontale) in part, and parietals 
{os parietale) and a median interparietal bone {os 
interparietale) (Fig. 2-7). Lateral support is pro- 
vided by petrous and tympanic portions of the 
temporal bone {os temporalis, pars petrosa et 
tympamca) and the wing of the sphenoid bone {ala 
sphenoidalis) (Fig. 2-2). The base of the braincase 
is formed by the sphenoid {os sphenoidale) and the 
occipital {os occipitale), which also forms the caudal 
limit of the neurocranium (Figs. 2-6, 2-8). The 
cribriform plate of the median ethmoid bone {lam- 
ina cribrosa, os ethmoidale) demarcates the rostral 
border of the neurocranium (Fig. 2-6). 
The brain {encephalon) of the European hamster 
has an average weight of 2.85 g in animals with a 
body weight of 450 g (Brauer and Schober, 1970). 
The following measurements were obtained from 
brains fixed in formalin: 
Brain length: 
29 
mm 
Brain width: 
18.5 
mm 
Brain depth: 
11.9 
mm 
Telencephalon length: 
23 
mm 
T T l_ * 1 il_ 
Hemispheric length: 
16.7 
mm 
Hypothalamus length: 
5.7 
mm 
Rhombencephalon length: 
11.4 
mm 
Cerebellum width with Pons: 
18.2 
mm 
Cerebellum width without Pons: 
15.3 
mm 
The European hamster has well- 
-developed cere- 
bral hemispheres {hemispheria cerebri) which are 
without sulci (lissencephalous) (Fig. 2-66). The 
olfactory bulbs {bulbi olfactorii) are relatively large 
and are overlapped caudally by the hemispheres to 
a depth of 5 to 8 mm. The cerebellum is about half 
as large as the cerebral hemispheres. The vermis 
cerebelli, the lobi paramediani and the lateral para- 
flocculi (Figs. 2-67, 2-68, 2-69, 2-70) are dis- 
tinctly developed. The large rami of the trigeminal 
nerve (n. trigeminus) and the optic chiasma {chi- 
asma opticum) are prominent on the ventral aspect 
(Fig. 2-69). 
2.19 HYPOPHYSIS 
The pituitary gland {hypophysis) (Fig. 2-70) 
lies in the sella turcica of the sphenoid bone, flat 
against the base of the brain between the trigeminal 
nerves. Caudally, it presses against the pons whose 
ventral surface it partly covers. The hypophysis 
also overlaps the cerebral crurae {pedunculi cere- 
bri) with the oculomotor nerve (n. oculomotorius) 
and the trochlear nerve {n. trochlears), as well as 
the mamillary body {corpus mamillare). At the 
ventrolateral edge of the hypophysis the abducens 
nerves {nn. abducentes) emerge. Also noteworthy 
is the large space between the hypophysis and the 
optic chiasma which is bridged by the tuber cine- 
reum. The hypophysis is positioned dorsal, and 
somewhat rostral, to the synchondrosis spheno- 
occipitalis (Fig. 2-71). At this position, trepanation 
is performed for hypophysectomy. The origins of 
the cranial nerves are similar to those reported for 
other rodents (Brauer and Schober, 1970; Horber, 
etal, 1974). 
The schematic longitudinal view of the hypo- 
23 
