906 PRACTICE OF AGRICULTURE. Part IH. 



canal in its structure does not differ from the sensible part of the stomach, having like that two plans of 

 muscular fibres, a circular and a longitudinal, by which its peristaltic motions are regulated ; the longitu- 

 dinal shortening the canal, and the circular diminishing its size. The alimentary part of the intestinal 

 canal ends with this small gut, which itself terminates abruptly in the ccecum or first of the large 

 intestines {fig. 619 a), and which intestine commences what has been termed g| y 



the excremeJititious canal. This entrance is effected in such a manner as 

 to leave, by a protrusion of its surface inwards, a kind of valvular appara- 

 tus, which prevents the return of the contents. 



5730. The large intestines {fig. ()\Qkk), in the horse are really deserving 

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

 mals they are little different from the small. They occupy and com- 

 pletely fill 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 

 s the human. 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 around 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. 616 m). By these means, the 

 matters are detained to be acted on more fully, and finally they are expelled in dry hardened balls. 



5731. 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 and molar muscles, through the arch of the palate in the form of a 

 bolus. Received 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 cesophagus 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 labor. 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 carnivorae. A dog fed 

 once a day will thrive, and when fed every other day only, will not suffer 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 food only at a time, which his digestive powers 

 peculiarly fit him to convert into nutriment quickly and efficaciously, by distributing the task through a 

 long tract of canal ; instead of confining it, as in man and the carnivore, to one simple organ, the 

 stomach. 



5732. The chyme passes into the duodenum from 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 in- 

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

 part of the intestinal tract, it is puriiosely 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 dtict, 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. 



5733. The liver may also be considered as a digestive organ {fig. 618 bh), 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 very 

 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 furnishgd 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 fcetal state, an- 

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

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

 he is seldom aflf'ected 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. 



5734. The pancreas is an assistant to digestion also, as we have reason to conclude by its pouring its con- 

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

 kidnev. 



5735. The spleen or milt, {fig. 618 d), is a spongy body situated at the greater extremity of the stomach, 

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

 the use of the stomach. 



5736. The kidneys are two excremental glands {e e) situated in the lumbar region, the right more ante- 

 rior than the left. In many brutes, as the ox, sheep, and hog, they are embedded in fat ; but in the 

 horse, dog, and the predatory tribes, they are seldom, so. The structure of the kidneys exhibits an ex- 

 ternal 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. 



5737. The urine appears to be a fcecal separation from the blood, and is in some measure connected with 

 the skin in its office. Thus, when the perspiration is great, the urine is less ; 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 th&n the human or those of most other animals ; and sub- 

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

 kiln-dried oats, &c., will produce diabetes. 



5738. 'The bladder of the horse {fig. Ql^i), is a membranous sac for the reception of the urine. It 

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

 its contents almost to the last drop. At its neck ^s 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 wreMm, which passes through the penis, and by that means ejects the urine. 



