18 THE EXTERIOR OF THE HORSE 



" rig" or ridgeling. In geldings the under surface of the scrotum is 

 marked by a depressed scar on either side of the middle line, resulting 

 from the operation of castration. 



The Sheath (fig. l). — The sheath is a loose portion of infolded 

 skin arranged in the form of a recess, into which the penis is retracted. 

 The infolded portion of integument is thin, supple, and devoid of hairs, 

 but largely supplied with sebaceous glands, which secrete an unctuous 

 matter for the lubrication of the penis. 



FEMALE 



The Vulva. — The vulva is the genito-urinary orifice of the female. 

 It is an elongated, vertical opening, placed below tlie anus. On either 

 side of it are two folds of skin and mucous memlarane, termed the 

 lahia or lips. When these are separated, a small globular organ is seen 

 lodged in a fold of mucous membrane at the lower part of the orifice; 

 this is the clitoris. 



During the period of heat, or sestrum, the labia, swollen and sensitive, 

 are repeatedly opened and closed, and the clitoris becomes momentarily 

 exposed and projected backward. 



7. FORE EXTREMITY 



The anterior limb or fore extremity extends from the withers above 

 to the foot below; it is united to the trunk l^y muscles extending along 

 the back, up the neck, and on to the walls of the chest and breast. It 

 presents for consideration a number of regions, as well as parts and 

 divisions of more or less importance. 



The regions of the front member comprise the shoulder, the arm, 

 the forearm, the elbow, the knee, the canon, the fetlock, the i^astern, 

 the coronet, and the foot, to which must be added the ergot. 



The Shoulder. — The shoulder is situated on the lateral aspect of 

 the chest, and forms the chief point of attachment of the fore-limb to the 

 trunk. In front it follows the line of the posterior extremity of the neck, 

 with which it unites. Behind, it is limited by a more or less prominent 

 muscular ridge extending down to the elbow. Above, it reaches as high 

 as the withers, and custom has fixed its lower limits at the elbow. It 

 must, however, be pointed out that wliat is commonly spoken of as the 

 shoulder embraces also the upper arm, and as these two parts are 

 intimately related and show no lines of demarcation, they may for con- 

 venience of description continue to be classed together. 



Shoulder Point (fig- l). — The shoulder point, as it is erroneously 

 termed, is the angular prominence corresponding to the shoulder-joint. 



