542 



RUMINANTIA. 



by the inferior thyroideal only, the superior 

 being distributed to the larynx. In the fore- 

 limb, a vascular twig, corresponding to the 

 interosseous artery^ is present both in the 

 Ruminants and Solipeda ; it is very voluminous 

 in the former, and but faintly marked in the 

 latter. The common carotids are remarkable 

 for their length in certain individuals ; the 

 most interesting peculiarity, however, obtains 

 in the presence of numerous anastomising 

 branches given off by, and tortuously inter- 

 communicating between the internal carotids. 

 It is this plexus which has been long known 

 under the name of rete mirabile, being situated 

 within the cavernous sinus on either side of 

 the sella turcica, and occasionally extending 

 backwards to join the vertebral artery. Simi- 

 lar appearances are found in Carnivora, and 

 in Cetacea where they are are not confined to 

 the region of the cranium ; many other ano- 

 malies of the same kind occur in other fami- 

 lies, the most striking being seen in the Sloth, 

 where the brachials and femorals are split up, 

 as it were, into numerous hair-like capillaries. 

 The spermatic artery is exceedingly large in 

 the Bull and twisted into a multitude of con- 

 volutions. In regard to the venous system of 

 ruminants we have only to remark that, ac- 

 cording to Weigel, valves are developed in the 

 portal vein.* 



Organs of respiration. The structural 

 modifications observable in this system de- 



Ffg. 



part so slightly from the ordinary mammi- 

 ferous type as scarcely to call for a separate 

 notice. The organisation of the larynx is 

 simple, its anterior ligaments and ventricles 

 being absent ; in many species the thyroid 

 cartilage is comparatively narrow. The tra- 

 cheal rings are for the most part incomplete, 

 and vary numerically in accordance with the 

 length of the neck.' According to Meckel 

 there are fifty in Moschus ; sixty in the Stag ; 

 seventy in the Chamois, Ox, and Sheep ; 

 eighty in the Llama ; and upwards of a hundred 

 in the Dromedary. We have counted ninety- 

 two in the Giraffe, where the length of the 

 trachea is between four and five feet ; in this 

 genus the epiglottis is short and thick, and 

 the arytenoid cartilages are remarkably large 

 and prominent, as in Ruminantia generally. 

 Occasionally there are three primary bron- 

 chial subdivisions ; when the trachea is simply 

 bifurcated, the right bronchus is paramount. 

 Most ruminants have the lung of the right 

 side separated into four lobes, and the left 

 into two ; in the Camel the right pulmonary 

 organ is double, while the left is single, and 

 exhibits no subdivision. The thymus gland is 

 extensively developed in this order and pro- 

 longed forward on either side of the trachea. 



Nervous system. The brain is elongated , 

 and more or less oval-shaped ; it is narrowed 

 anteriorly in the Sheep, and somewhat abrupt 

 in this direction in Cervidae (fig. 365.). Con- 

 365. 



Brain of the Giraffe. (From Owen.) 



sidered in reference to the bulk of the animal 

 the brain is significantly small in this order, 

 as in Pachydermata and Solipeda. Its weight 

 in the Ox is only one-fourth of the human 

 brain, although the body of the former is six 



* Weigel, de strato muse, tunicas venarum me- 

 dia}, etc., p. 31. Leips. 1823. 



times larger than that of the latter; virtually, 

 therefore, the brain in Man is twenty-four 

 times greater than in the Ox (Monro). The 

 proportionate weight of the cerebrum as com- 

 pared with the cerebellum and medulla oblongata, 

 is likewise less considerable in ruminants ge- 

 nerally than in the human subject. The cere- 

 bral convolutions are numerous and tolerably 



