286 THE HORSE. 



whipcord under the finger. These several parts are connected 

 together by cellular membrane and covered by the two layers of 

 reflected peritoneum, namely, the tunica vaginalis and tunica vagi- 

 nalis reflexa, by the thin layer of cremaster muscle, as well as by 

 a fourth investment, a continuation of the superficial fascia of the 

 abdomen. All these parts must be divided before the eanal is 

 reached, for operating in castration. 



The female organs of generation are essentially the ova- 

 ries, the uterus and its appendages forming the bed in which the 

 embryo is nurtured to maturity. The ovaries are two small oval 

 bodies, about the size of large walnuts, situated behind the kid- 

 neys, and having the fimbriated extremities of the fallopian tubes 

 hanging loosely adjacent to them. These tubes, one on each side, 

 terminate in the uterus, which is of a remarkable shape in the 

 mare. It consists of a body and two horns. The body has a 

 mouth, or os, which opens into the end of the vagina, while, in 

 itself, it is oblong, and in the unimpregnated state it is entirely 

 contained within the pelvis. Anteriorly it divides into two burns 

 (cornua), which diverge towards the loins, turning upwards, and 

 lying under the wings of the ossa ilii (see fig. facing p. 251). They 

 terminate in rounded extremities. Each cornu receives the fallo- 

 pian tube of its own side, the opening being so small as scarcely 

 to admit a silver probe. The vagina lies between the bladder and 

 rectum, and is about eighteen inches in length ; it is lined with 

 mucous membrane, and surrounded with muscular fibres, which 

 form the sphincter vaginas. 



CHAPTER XVIII. 



THE NERVES AND SPECIAL ORGANS. 



The Nerves — The Organ of Smell — The Eye — The Ear — 

 The Organ oj Touch — The Foot. 



THE NERVES. 



The nervous system may be compared to the fuel that 

 heats the water of the steam-engine, and converts that apparently 

 most simple and innocent fluid into the powerful agent which is 

 capable of developing almost any amount of force. This fuel, 

 however, is itself inactive until it is endowed with life by the 

 agency of fire; and, in the same way, the nervous system of the 

 animal being must be provided with the living principle, of whose 

 nature we can only judge by its effects when present, and by the 

 cessation of all action when absent. There are many processes 



