834 THE NERVOUS SYSTEM OF THE OX 



The following paired plexuses are derived mainly from branches of the coeliac 

 and aortic plexuses: 



1. The renal plexuses (P. renales) proceed largely from the cceliaco-mesenteric 

 ganglia, but receive fibers also from the small splanchnic nerves. They enlace the 

 renal arteries and supply the kidneys. Minute renal ganglia occur on the course 

 of the nerves along the renal vessels. 



2. The adrenal plexuses (P. suprarenales) are formed by a relatively very 

 large number of fine fibers derived in great part directly from the cceliaco-mesen- 

 teric ganglia. Numerous minute ganglia occur in their meshes. 



3a. The spermatic plexuses (P. spermatid) proceed from the aortic plexus 

 and branches from the posterior mesenteric ganglion. Each accompanies the 

 corresponding (internal) spermatic artery to the testicle. 



3&. The utero-ovarian plexuses (P. ovarici) are the homologues in the female 

 of the preceding. They accompany the utero-ovarian arteries to the ovary and the 

 cornua of the uterus. 



The pelvic plexuses (P. hypogastrici) are the pelvic continuations of the aortic 

 and posterior mesenteric plexuses. Two or more nerves proceed from the posterior 

 mesenteric ganglion and enter the pelvic cavity ventral to the large vessels, anasto- 

 mose with each other and with branches from the sacral nerves — especially the 

 third and fourth^and ramify on the pelvic viscera. The peripheral plexuses 

 derived therefrom are named according to the organs which they supply; the chief 

 of these are the haemorrhoidal, vesical, utero-vaginal, prostatic, cavernous (of the 

 penis or clitoris) (P. hsemorrhoidalis, vesicalis, uterovaginalis, cavernosus penis s. 

 clitoridis, etc.). Others enlace the arteries (P. iliacus, femoralis, etc.). 



THE NERVOUS SYSTEM OF THE OX^ 



The spinal cord resembles that of the horse in conformation and structure. 

 In cattle of medium size its length is about 165 to 170 cm. (ca. 65-67 inches), and 

 its weight about 240 to 250 grams (ca. 8 ounces). 



In a cow 140 cm. in height Dexler found the weight of- the cord (including the intradural 

 nerve-roots) to be 260 gm. and the length 162 cm. The lengths of the regions were: cervical 41 

 cm., thoracic 72 cm., lumbar 32 cm., sacral 7 cm. 



The brain has an average weight of about 500 grams (ca. 16-17 ounces). 

 Its differences in general form are correlated with those noted in the consideration 

 of the cranial cavity. 



The medulla oblongata is short, wide, and thick. Its ventral face is strongly 

 convex. The pyramids are narrow, short, and close together in front. Near the 

 decussation there is a well-defined oval prominence on either side which indicates 

 the position of the posterior olive. The corpus trapezoideum is large; it has no 

 central part between the pyramids. The external arcuate fibers are distinct. The 

 restiform bodies are short and thick and diverge more strongly than in the horse. 

 The floor of the fourth ventricle is only about two-thirds as long as in the horse. 

 The area acustica is a well-marked oval prominence lateral to the middle part of 

 the limiting sulcus. The tuberculum acusticum at the origin of the acoustic nerve 

 is very large. The anterior fovea is distinct. The posterior recess of the fourth 

 ventricle communicates through a median aperture (Apertura mediana)^ with the 

 subarachnoid space. 



1 Only the most salient differences as compared with the horse will be mentioned. 

 ^ Also known as the foramen of Magendie. 



