80 STRUCTURE AND ECONOMY OF THE HORSE. 



It first takes a course from the neck of the bladder backwards, 

 and becomes increased in size, and approaches very near the 

 skin, being, indeed, just under the anus ; it then forms an acute 

 ano;le, turninix downwards and forwards, and is here surrounded 

 by a muscle called the accelerator urma3, and contmues to the 

 extremity of the penis. 



In the female the passage is considerably shorter, being about 

 two inches backward, and slightly upward, when it opens into 

 the pudendum, and is connected with the organs of generation. 



The Uriiie is a fluid secreted or separated by the kidneys, 

 and poured by them through specific channels, the ureters, into 

 the bladder. In a state of health it is of an amber colour, and 

 its peculiar odour is well known. It is composed chiefly of 

 Avatcr, which contains some salts, and a peculiar substance, 

 called urea, to which its properties are more partioilarly owing. 

 The colour of the urine is much lighter after a large quantity of 

 water has been drunk ; and darker, and more acrid, after solid 

 food. There is a great sympathy between the kidneys and the 

 skin ; as the secretion of the one increases, that of the other 

 diminishes : when horses sweat much, they urine little, and vice 

 versa. The urine is separated from the blood, which is conveyed 

 to the kidneys by the emulgent arteries ; these organs, therefore, 

 serve the purpose of separating the excrement from the system, 

 and conveying it away : and it is also thought they serve an 

 oflice subordinate to the skin, — that of removing the superfluous 

 fluid that is not actually required by the skin, or cooling the 

 body by means of perspiration. 



The Bladder, is, of course, a reservoir for the urine, preventing 

 the great inconvenience that would result from discharging the 

 tu'ine as fast as it is secreted. It receives the urine by means 

 of the ureters, and suffers it to accumidate to a certain degree, 

 differing in different individuals : it then pi'oduces an uneasy 

 feeling, which induces the animal to discharge it. The act of 

 staling is therefore a voluntary act, but the inclination urging 

 it is much affected by nervous influence ; e. g. fear, and anxiety 

 of mind, will repeatedly cause a disposition to urinate, both in 

 the horse and in man. 



The act of staling is more simple in the mare than in the 

 horse ; and in the former a retention of urine is much rarer, 

 and is more easily removed, which is owing to the straightness 

 and shortness of the canal in mares, and the great length and 

 obliquity of the external passage in horses. 



In the urinary act the horse stretches out his legs, and after 

 a few moments' preparation, in which he inspires a greater quan- 

 tum of air than common, he expels the urine by the conjoint 

 assistance of the diaphragm, the abdominal muscles, and muscular 

 coat of the bladder. Towards the conclusion of the act, the 



