THE HORSE. 



61 



every veterinary student should aim to be 

 well acquainted vv^ith ; it is a part that seems 

 to be, in this country, more liable to anchy- 

 losis and exostosis than any other region ; 

 here is the seat of spavin, and no one can 

 possibly understand the nature of such dis- 

 ease unless he be conversant with the ana- 

 tomical mechanism of the hock. The hock 

 corresponds to the tarsus or instep of man, 

 and is composed of six bones, viz., os calcis, 

 astragalus, os cuboides, ossa cuneiformis ; 

 which comprise three small bones, viz., ex- 

 ternal, internal, and middle cuneiforme. We 

 shall first consider the os calcis. 



Q. What is the situation of the os cal- 

 cis ? — A. It forms the posterior projec- 

 tion known as the point of the hock — the 

 superior and posterior bone of the tarsus. 



Q. Give a general description of the 

 bone. — A. Its figure is irregular ; presents 

 a body, tuberosity, posterior surface, and 

 base ; the body is most bulky at its inferior 

 part ; as a whole, it is irregularly convex ; 

 concave and expanded at its base, where 

 it presents four surfaces for articulation 

 with the astragalus ; the tuberosity is ob- 

 long, flattened on each side, and terminates 

 in a rough tubercle, into which is inserted 

 the tendons of the gastrocnemii. It is sit- 

 uated on the superior part of the hock. 



THE KNUCKLE BONE (aSTRAGALUs). 



Q. What is the situation of the astra- 

 galus ? — A. It is situated in the superior 

 part of the hock, and is the principal sup- 

 port of the tibia. 



Q. How do you distinguish it from 

 other bones ? — A. It is readily distin- 

 guished by its double pulley-like articula- 

 tory surfaces, which consist of two semi- 

 circular prominences, having between them 

 a deep groove, well adapted to receive the 

 projection found on the inferior extremity 

 of the tibia. 



Q. What is the appearance of the pos- 

 terior surface ? — A. It has four articulatory 

 surfaces, corresponding to those of the os 

 calcis. 



Q. What is the appearance of the base 

 or inferior extremity ? — A. It has an irre- 



gularly flattened articulatory surface, which 

 comes in contact with the large cuneiform 

 bone. 



CUBOID BONE (oS CUBOIDEs). 



Q. What is the situation of the cuboid 

 bone ? — A. On the outer part of the 

 hock. 



Q. How is the bone divided ? — A. Into 

 four surfaces, viz., external, internal, supe- 

 rior, and inferior. 



Q. How do you distinguish the external 

 from the internal surface ? — A. The exter- 

 nal surface is broad, irregular, curved, and 

 roughened ; on the other hand, the internal 

 is excavated, and has three articulatory 

 smfaces. 



Q. How does the superior surface differ 

 from the inferior ? — A. The superior sur- 

 face has two articulations, with a fossa 

 between them ; the inferior surfaces are 

 smaller, and correspond, one to the articula- 

 tory head of the splent bone, and the other 

 to the cannon. 



large cuneiform bone (os cuneiforme 

 magnum). 



Q. What is the situation of the cunei- 

 form bone ? — A. Directly beneath the 

 astragalus. 



Q. What is the appearance of this bone ? 

 — A. It presents a triangular form ; its 

 acute termination being in a posterior direc- 

 tion, it has superior and inferior surfaces, 

 sides, and angles. 



Q. How is the superior surface distin- 

 guished from the inferior ? — A. The supe- 

 rior surface has a uniform articulatory 

 surface, with the exception of a small, 

 rough grove running to its centre, from the 

 outer side, which terminates in a central 

 pit. The inferior sm-face is rather convex, 

 yet presenting a flat appearance ; its poste- 

 rior angle has an articulatory surface, cor- 

 responding to that of the cuboid bone. 



Q. What are the articulations of this 

 bone? — A. It articulates with the astra- 

 galus, cuboid, middle and small cunei- 

 form bones. 



