440 ANGIOLOGY. 



The CORONARY PLEXUS surrounds the os coronse and upper part 

 of the os pedis. Extending backwards below the lateral cartilages, 

 the plexus consists of an anterior or middle, and two lateral por- 

 tions. The middle coronary lies in front of the foot, and receives 

 the anterior ascending branches of the laminal plexus. The lateral 

 coronary plexus consists of a superficial and a deep portion, the 

 former situated upon, the latter under, the lateral cartilage, and 

 formed by the posterior branches of the laminal, the deep one 

 being joined by veins from the coronet, and from the ligaments 

 and tendons of the region. The veins of the frog extend over 

 the external surface of the sensitive frog, ascend the sides of the 

 lateral cartilages, and unite to form a large vein, which, with 

 branches from the superficial and deep coronary plexuses, runs 

 up the lateral aspect of the os coronse, all uniting near its head 

 to form the digital vein. 



The internal or interosseous veins of the foot form a system 

 of satellites to the circulus arteriosus and its branches. They 

 pass out of the bone through the plantar foramina, at each side 

 of the tendinous surface ; thence up the inner side of the lateral 

 cartilages, finally uniting with the branches of the deep coronary 

 plexus. 



DIGITAL VEINS. 



The digital veins, formed by the union of the deep and 

 superficial coronaries, and veins from the frog, ascend the digit 

 in company with the arteries and nerves, and terminate a little 

 above the fetlock, by uniting to form an arch between the flexor 

 tendons and suspensory ligament. From this arch, the sesamoi- 

 dean, spring the three metatarsal veins. The digitals receive 

 branches corresponding to the perpendicular and transverse divi- 

 sions of the arteries, as well as twigs from surrounding structures. 



METATARSAL VEINS. 



The metatarsal veins are three in number, internal, external, 

 and deep, originating in the sesamoidean arch. The internal is 

 the largest, and appears to be a continuation of the internal 

 digital. It passes up the cannon bone, internal to, and a little 

 in front of, the flexor tendons, accompanied by the internal 

 metatarsal nerve. Nearing the hock, it crosses obliquely to the 

 anterior surface of the joint, where it communicates by a large 



