Book VII. PHYSIOLOGY OF THE HORSE. 975 



terminates abruptly in the ccecum or first of the large intestines (Jig. 834 a), and which intestine com- 



mences what has been termed the excrementitious canal. This entrance 

 is effected in such a manner as to leave, by a protrusion of its surface 

 inwards, a kind of valvular apparatus, which prevents the return of the 

 contents. 



64()3. The large intestines (Jig. 831. k k) in the horse are really deserving 

 of that name, being very capacious; while in man and carnivorous animals 

 they are little different from the small. They occupy and completely till 

 up the lower portion of the abdomen : the ccecum occupies the right side 

 and carries its blind end towards the diaphragm, which is not furnished 

 with an appendix as in man. A careful inspection of this intestine will show that the appellation of 

 excrementitious canal does not wholly apply to it: but that, on the contrary, it performs some of the 

 offices attributed to the smaller intestines. The colon commences small from the side of the base of the 

 ccecum ; but soon enlarging, it makes a turn round the abdomen, when contracting it ends in the rectum, 

 and passes backwards to the anus. Along the course of the large intestines are muscular bands, which 

 throw their surfaces into folds, and also form them into a continuation of cells (fig. 831. m). By these 

 means, the matters are detained to be acted on more fully, and finally they are expelled in dry 

 hardened balls. 



6404. The digestive process in the horse is one of the most curious as well as one of the most important 

 which goes on in the body. The various actions of an animal body produce relaxation and waste, which 

 are indicated by fatigue and hunger. To restore the one, rest is required, and to restore the other, food 

 becomes necessary. For the herbivorous tribes, vegetable matter is sought for, which being collected, is 

 masticated by the grinders and mixed with saliva, until it becomes a softened mass, when it is passed 

 backwards by the tongue ajid molar muscles, through the arch of the palate, in the form of a bolus. Re- 

 ceived into the pharynx, which rises to receive it, and the action of which forces down the epiglottis, all 

 impediment is removed to its falling in the open funnel of the oesophagus; which having received it, the 

 spiral fibres of the oesophagus force it inwards into the stomach. While the food remains within the 

 cuticular part, it is acted on by pressure ; but being further removed, it meets the action of the gastric 

 fluid, by which it is reduced to a pultaceous mass called chyme. In this state it is passed into the small 

 intestines : for in the horse, as before observed, the process of digestion is by no means completed in the 

 stomach, as in man and many animals. The exertions of the horse require that he should eat largely and 

 nutritiously, but the bulky viscera of the ox would have ill suited with his necessities; for he is not 

 only strong, but his motions are designed to be quick also : it was therefore necessary that some speciality 

 should occur to meet these seeming discordances. This consists in the mode of digestion, which being but 

 partially completed in the stomach, requires a less bulk in that organ, the intestines participating in the 

 labour. A horse will eat two or three pecks of corn or ten pounds of hay at a meal, and yet in a natural 

 state his stomach will not hold half of either. He will also drink two pails of water, when the same organ 

 cannot hold one. What is taken into the stomach is therefore quickly passed through it, and more is 

 required. A horse cannot fast long without injury and pain ; his food does not produce a lasting effect in 

 the constitution as animal food does on the Carnivora. A dog fed once a day will thrive, and, when fed 

 every other day only, will not sutler materially; but no horse fed once a day would support himself: even 

 oxen and sheep, as having a slower digestion and more intestinal room, can bear fasting better than the 

 horse. As an animal destined for quick as well as great exertions, his wants prompt him to take in a 

 moderate portion of tood only at a time, which his digestive powers peculiarly tit him to convert inio 

 nutriment quickly and efficaciously, by distributing the task through a long tract of canal ; instead of 

 confining it, as in man and the Carnivora, to one simple organ, the stomach. 



6405. The chyme passes into the duodenum Jrom the stomach, where it receives the addition of the pan- 

 creatic and biliary fluids, whose ducts open into that part of the intestinal tracts. Conducted onwards by 

 the creeping peristaltic motion, it passes through this long alimentary tract rather rapidly in the horse ; 

 but it remains sufficiently long to receive further additions from the secreting surfaces of the smaller 

 intestines, and probably to have its work of division and absorption begun in it. Arrived at the larger 

 part of the intestinal tract, it is purposely delayed to be fully strained and separated, the open mouths of 

 the lacteals spread over the villous surface receiving the nutritious part under the name of chyle, and the 

 residue being carried backward, and thrown out as dung. The chylous orifices belong to minute tubes 

 termed lacteals, which pass onwards enveloped in membranous folds termed mesentery, until uniting in 

 one trunk called thoracic duct, their contents are poured into the heart, whereby they become mixed 

 with and converted into blood, producing an increase to its quantity ; as the alteration it receives in the 

 lungs is an amelioration of its quality, which it has been shown is equally necessary to the animal. 



6t06. The liver may also be considered as a digestive organ (fig. 833. It b), inasmuch as it secretes a fluid 

 whose office appears to be to quicken the action of the intestines ; at the same time that perhaps the vei y 

 matter separated tends to purify that blood which has been already distributed to the chylopoetic viscera. 

 All other animals, except the horse, ass, and deer, are furnished with a receptacle for the bile, where it 

 may be retained and rendered more acrid : but the horse has no gall bladder, and, in his foetal state, 

 another speciality presents itself in this organ, which is, that he is deprived of a canalis venbsus, and thus 

 the whole of the abdominal blood flows through the liver. From this simplicity of structure in the horse 

 he is seldom affected with obstructed or concrete bile ; but the organ itself is liable to inflammation, and 

 also to a chronic disease of it through the medium of the stomach. 



6407. The pancreas is an assistant to digestion also, as we have reason to conclude by its pouring its 

 contents into the duodenum with the bile. It is situated behind the liver, between the stomach and left 

 kidney. 



6408. The spleen, or milt (Jig. 833. d), is a spongy body situated at the greater extremity of the stomach. 

 Its use is likewise not clearly ascertained ; but it has been supposed to be that of a reservoir of blood for 

 the stomach. 



6409. The kidneys are two excremenfal glands (ee) situated in the lumbar region, the right more forward 

 than the left. The structure of the kidneys exhibits an external reddish part, an internal whitish part, 

 and a cavity called the pelvis. From this cavity passes out the duct called the ureter, and brings with it 

 the urine which is secreted within the kidney. The ureters convey the urine to the bladder. 



6410. The urine appears to be ajwcal separation Jrom the blood, and is in some measure connected with 

 the skin in its office. Thus, when the perspiration is great, the urine is Uss; and on the contrary in winter, 

 when the perspiration is small, the urine is more considerable. The kidneys of the horse are more easily 

 stimulated into increased action by diuretics than those of man or of most other animals ; and substances 

 which would not appear potent act with violence on his urinary organs. Thus mow burnt hay, kiln-dried 

 oats, &c, will produce diabetes. 



6411. The bladder of the horse (fig. 833. i) is a membranous sac for the reception of the urine It rests 

 on the pubis, and is immediately under the rectum. It is in part muscular, by which it can expel its 

 contents almost to the last drop. At its neck is a kind of sphincter to prevent the involuntary escape of 

 urine, and at its posterior part it is pierced by the ureters. To the bladder is attached a membranous pipe 

 called the urethra, which passes through the penis, and by that means ejects the urine. 



Subsect. 14. The Foetal Colt. 



6412. The reproductive system is one of the most important of nature's works ; and, whether vi examine 

 the subject anatomically or physiologically, we shall be convinced that the utmost wisdom and care have 



