764 



Dvsri;rsi.\, 



auiinals (polypi, &c.) f.iul, in the medium iii which 

 they live, and from which they directly receive them. 

 tlie principles serving t'or ilicir composition. Tlie 

 decomposition of animal and vegetable mailer in the 

 soil prepares the aliiiient or nutritive principle of 

 vegetables, which, being held in solution by \\;iirr. 

 is absorbed by Uieir roots. In all these beings there 

 are no digestive organs or functions. The prepara- 

 tion of their nutriment is effected by physical opera- 

 tions exterior to themselves, and over which they 

 liave HO control. In tlie higher or complete animals, 

 or in man, the case is very tlitl'erent. Nature does not 

 pv-eiit to them tlie nutritive elements in a state fitted 

 to be introduced, at once, into tlie interior organism, 

 and to be employed in its composition. Their aliment 

 cou>isis of Uie nutritive principles in a compound 

 state, intimately combined with other substances, from 

 which they require to be disengaged. This is accom- 

 I'li-hcil by the animal itself, which is provided with 

 es|>ecial organs or apparatus and functions for this 

 purpose. Digestion, then, consists in the disengage- 

 ment of tlie nutritive elements from their combina- 

 tions, and their reduction to the molecular state, 

 admitting their introduction into the vessels, and 

 t heir diffusion throughout the organism, for the pur- 

 poses of its composition. It is a process analogous 

 to the decomposition of the aliment of vegetables in 

 the soil, and is affected, like all decompositions, by 

 analogous or chemical operations. In this class, the 

 procuring of the aliment is the act of the animal, 

 depending on its voluntary powers, and is controlled 

 by a great variety of circumstances, affecting the 

 quantity and quality of the food. 



The organs composing tlie digestive apparatus in 

 man are numerous. They are the mouth, armed 

 with teeth, for mechanically breaking down tlie food 

 by mastication ; the salivary glands, furnisliing a 

 fluid intimately combined with the food, in mastica- 

 tion, and collected in the stomach, which is its reser 

 voir ; tlie pharynx, a muscular and membranous bag, 

 for the reception of the masticated bolus from tlie 

 nit null ; tlie oesophagus, a muscular and membranous 

 tube, for conducting the bolus into the stomach ; the 

 stomach, a muscular and membranous bag, or en- 

 largement of the alimentary canal, secreting a fluid 

 or fluids, and a reservoir of tlie salivary and other 

 secretory fluids of the interior surfaces, and in which 

 the food is subjected to the decomposing process, 

 until reduced to a pulpy mass, called chyme, consist- 

 ing of the nutritive and innutritive elements, in a 

 state of mechanical mixture ; the duodenum, or 

 second stomach, in which the chymous mass is sub- 

 mitted to the action of the biliary and pancreatic 

 fluids, and in which the nutritive elements begin to 

 separate from the innutritive matters, and to be 

 absorbed by the lacteals, the roots of the animal 

 economy ; the liver and pancreas, furnishing bile 

 and a species of saliva, which are mixed with, and 

 acton, the chyme in the duodenum ; the jejunum and 

 ileuin, or small intestines, in the course of which 

 the separation, begun in the duodenum, is com- 

 pleted, and nearly the whole of the nutritive prin- 

 ciples forming chyle are absorbed ; and, lastly, 

 the large intestines, a reservoir for all the excre- 

 mentitious principles, and which, in it, are con- 

 verted into fieces. The whole of these organs 

 compose the apparatus of digestion, but all are 

 not of equal importance. The stomach and duo- 

 denum are the most eminent organs, and those 

 whose condition exercises the greatest influence over 

 the powers of digestion. This apparatus is intimately 

 connected, and a natural state of each of its parts, 

 and a due exercise of the function of each, are essen- 

 tial to the'healthy, undisturbed performance of diges- 

 tion. This connexion is maintained through the 



ganglioiiary system of nerves, which not only unites 

 I iiesc organs together, but combines them with nil 

 their congeries, appropriated to tlie perfect elabon- 

 i inn of tlie nutritive and sustaining principles of the 

 economy. The stomach is tlie centre of tlie diges- 

 tive apparatus, and may be regarded in nearly the 

 same view, for the whole of the organs connet -teil 

 with individual nutrition. It owes this diameter tc 

 its intimate union with tlie great solar plexus, (he 

 centre or brain, if it may be so termed, of the | 

 lionary system, regulating tlie nutritive function-*, it 

 is also immediately associated with the brain, 

 through the medium of the eighth pair of pneun.o 

 gastric nerves, and thus is placed in relation with 

 the exercise of the moral and intellectual faculties. 

 The stomach is consequently exposed to be disordered 

 in its functions by violent impressions from these 

 faculties, as they are also liable to be affected by the 

 disordered conditions of the stomach. It is neces- 

 sary to have these diversified connexions pointed out. 

 to possess a clear understanding of tlie numerous and 

 very different sources from wliich disturbances reach 

 tlie process of digestion. 



A few words will now be necessary as to digestion 

 itself. It is not all substances that are fitted for 

 aliment, and are susceptible of digestion. Food is 

 intended for the renovation of the body. It must 

 consist of the same elements as the animal structure, 

 and be capable of becoming organized and living. 

 It must then contain, at least, three elementary 

 animal principles hydrogen, carbon and oxygen ; 

 and much of it contains, also, a fourth azote. These 

 elements form secondary compounds, in which state 

 alone they constitute aliment ; such are albumen, 

 fibrin, gelatin, osmazome, oil, engan, farina, mucil- 

 age, and other animal and vegetable compounds. In 

 all these substances, tlie molecules are easily separable 

 without being chemically decomposed, which is one 

 of the primary requisites of digestibility, and to effect 

 which the chief object of digestion. The masticated 

 and insalivated food passes into the stomach. Here 

 it is macerated in the saliva collected in tlie stomach, 

 and in the proper liquid secreted by the villi of tlie 

 gastric mucous membrane, at a temperature of 104 

 Fahr. This liquor is called gastric juice. Its true 

 nature is not accurately determined, but, as far as 

 examination has ascertained, it resembles saliva 

 mixed with a small portion of lactic or muriatic acid. 

 The stomach, in a healthy state, always contracts 

 on its contents, so that its parietes, in digestion, are 

 always in contact with the food. During digestion, 

 the stomach has a constant vermicular motion, its 

 muscular fibres contracting, successively, from the 

 smaller to the larger end. The food is thus agitated, 

 acquires a rotatory movement, and is mingled with 

 the fluids of the stomach. In a short time, the 

 change accomplished in the stomach commences ; 

 it becomes pulpy, and then reduced to a semifluid of 

 a light, grayish colour. From the uniform pressure 

 of the stomach, the solid and most resisting portions 

 are forced into the centre, while the digested and more 

 fluid matter is found on the surface, and is gradually 

 carried by the contraction of the muscular fibres, 

 into the duodenum. 



Mr Plulips and others have been led to suppose, 

 from this circumstance, that the food in contact with 

 the parietes of the stomach was alone digested ; but 

 it is a mere physical result, as uniform pressure in 

 every direction, on a mass of different consistency, 

 will always drive the most fluid to the circumference. 

 The pulpy, grayish substance resulting from the 

 stomachic digestion is called chyme, (q. v.) When 

 examined with the microscope, the writer of this 

 article has always found it to consist of an immense 

 number of transparent globules, of various sizes, inter- 



