[Proc. Koy. Soc. Victoria, 23 (N.S.). Pt. I., 1910. 



Aki. Vll. — A Study of the Guttural Fouches of Horse. 



By WALTER STAPLEY, M.D., M.R.C.V.S. 



(Lecturer on Veterinary Anatomy and Surgery, Melbourne University). 

 [Read 26th May, 1910.] 



A knowledge of comparative anatomy is apt to induce the 

 belief that many of the variations of structure existing in dif- 

 ferent species of animals is due to some form of force operat- 

 ing on animal tissues. An. excellent example of force dominat- 

 ing shape is displayed in the thorax of the horse. The weight 

 of the horse is largely carried on the sides of the ribs, from 

 which results a lateral narrowing of the thorax and a driving 

 backward toward the loin, of the lung ; consequently it becomes 

 necessary for the horse to carry eighteen pairs of ribs, so that 

 the thoracic content may be accommodated. Man's upright 

 position has removed lateral, restricting forces from the sides 

 of his chest; the lightness of lung tissue, unrestrained by such 

 pressure, has caused the human lung to encroach on the neck. 

 It is noteworthy that with ascent of the lung in tlie neck only 

 twelve pairs of ribs are found, and the last or lower rib usually 

 showing atrophic changes. 



Cervical ribs are occasionally found in men and in women ; 

 they are, however, reported to be three times as common in 

 women as in men. AVhether they exist in aboriginals I do not 

 know. The fact that the costal breathing of cultured women is 

 said not to occur in native races leads me to think that in all 

 probability cervical ribs are conuiionly found associated witli 

 atrophy of the upper limb. Sui'geons have removed these neck 

 ribs for the relief of pain. This pain is regarded to arise from 

 stretching of the brachial plexus and the subclavian artery ; 

 it is not improbable that pain may occur during the develop- 

 ment of these structures from an irritated pleura. From this 

 irritated pleura arises the demand for a rib to protect the un- 

 protected lung, and the pain arising from the same source 



