850 THE NERVOUS SYSTEM OF THE DOG 
9. The cruciate fissure is the deepest and most characteristic. It cuts deeply into the an- 
terior third of the dorso-medial border and runs almost straight outward. It is continuous on the 
medial surface of the hemisphere with the calloso-marginal or splenial fissure. 
10. The sulcus rhinalis is continued on the tentorial 
surface of the hemisphere by the occipito-temporal fissure. 
Anteriorly it is prolonged as the olfactory fissure, which 
is concealed by the olfactory bulb and tract. . 
11. The calloso-marginal fissure usually consists of 
two parts, splenial and genual. The splenial fissure is 
parallel with the splentum and middle part of the corpus 
callosum on the medial surface of the hemisphere. It is 
continuous in front with the cruciate fissure and runs for- 
ward and outward across the tentorial surface to join the 
occipito-temporal or calearine fissure. It gives off from 
its highest part the short accessory cruciate fissure. The 
genual fissure is approximately parallel with the genu of 
the corpus callosum. 
12. The suprasplenial fissure runs almost parallel 
with the posterior part of the calloso-marginal fissure on 
2 the inner and tentorial surfaces of the hemisphere. 
d; hippocampal fissure} ¢), sulcus cCrporis 13. The occipito-temporal or calcarine fissure is the 
callosi; f, postsplenial fissure; 9, lesser Continuation on the tentorial surface of the hemisphere of 
the splenial fissure. 
14. The hippocampal fissure forms the medial 
boundary of the piriform lobe. 
Fic. 681.—Ricutr CereBRAL HEMISPHERE 
or Doc; Meprau VIpw. 
1, Corpus callosum; 1’, genu; 1’’, splen- 
ium of corpus callosum; a, genual fissure; 
b, splenial fissure; c, suprasplenial fissure; 
cruciate fissure; h, cruciate fissure. (After 
Ellenberger, in Leisering’s Atlas.) 
The olfactory bulb is large and is compressed laterally; its anterior end pro- 
jects beyond the frontal pole of the hemisphere. The tract is short and is also 
flattened laterally. Both contain a narrow cavity which communicates with the 
lateral ventricle. The piriform lobe is large and rounded. 
The cranial nerves present the following special features which are worthy of 
notice: 
The ophthalmic nerve gives off frontal, long ciliary, ethmoidal, and mfratro- 
chlear branches. The lacrimal nerve arises from the ophthalmic at its origin;! its 
recurrent branch emerges at the orbital ligament and concurs with the zygomatic 
and frontal nerves in the formation of the anterior auricular plexus. The frontal 
nerve emerges from the orbit in front of the upper end of the orbital ligament, 
ramifies in the upper lid and the adjacent skin of the forehead, and sends branches 
backward to the anterior auricular plexus. The long ciliary nerve accompanies 
the optic nerve and divides into several branches which pierce the posterior part of 
the sclera. The ethmoidal nerve gives off internal nasal branches and ends in the 
muzzle. The infratrochlear nerve runs forward between the medial straight and 
the superior oblique muscles of the eye and ramifies on the face in the vicinity of 
the medial canthus. 
The maxillary nerve emerges through the foramen rotundum and gives off 
five branches. The lacrimal nerve emerges from the orbit lateral to the frontal; 
its branches concur with the frontal and auriculo-palpebral nerves in the formation 
of the anterior auricular plexus. The zygomatic nerve emerges through an opening 
in the upper part of the orbital ligament and ramifies in the lower lid and on the 
adjacent surface of the face. The infraorbital nerves, two in number, divide within 
the infraorbital canal and after their emergence upon the face, thus forming seven 
or eight external nasal and superior labial branches. The sphenopalatine nerve 
gives off lesser and greater palatine and posterior nasal nerves. 
The mandibular nerve passes out through the foramen ovale. The superficial 
temporal nerve divides into auricular, temporal, and malar branches; the last- 
named crosses the masseter and ramifies with the buceal nerves. (The mylo-hyoid 
nerve is given off from the mandibular nerve almost immediately after the latter 
emerges from the cranium; it innervates the mylo-hyoideus and occipito-mandib- 
ularis and gives off a branch which turns around the lower jaw, joins the inferior 
1The origin of the lacrimal nerve is such that Ellenberger-Baum and Martin describe it 
as a branch of the maxillary nerve. 
