PHYSIOLOGY. 



The description of this fluid will be found 

 under the article CHYLE. Its progress 

 through the intestine is retarded by 

 the numerous convolutions of the tube ; 

 and the chyle, separated from the 

 excrementitious part of the food, is 

 brought into contact with the inhaling 

 orifices of the lacteals, that commence, 

 according to Lieberkiihn and other mi- 

 croscopical observers, by patulous orifices 

 on the surface of the villi. The latter 

 projections, so named from a comparison 

 with the pill of velvet, are very nume- 

 rous on the circular projecting folds of 

 the internal coat, called valvulae conni- 

 ventes. These latter not only render the 

 progress of the chyle slower, but increase 

 very greatly the absorbing surface, and 

 penetrate, in consequence of the intesti- 

 nal contractions, into the midst of the 

 chyle, in quest of its nutritive particles. 

 A fluid is secreted from the intestine, 

 analogous to that furnished by the sto- 

 mach, jfihough an accurate examination 

 oTits .nature and properties is one of the 

 physiological desiderata (succus intesti- 

 nal].;). At the same time that the absorp- 

 tion of the chyle from the villous surface 

 of the intestine is going on, it is moved 

 gradually downwards, towards the large 

 XnTestine, by the peristaltic motion. This 

 is an undulatory and gentle -constriction, 

 taking place in 'several parts of the tube 

 at once, and producing therefore a singu- 

 lar appearance, compared to the crawling 

 of worms, and hence termed vermicular. 

 It moves the chyle repeatedly over the 

 surface of the intestine ; and though it 

 must urge that fluid partially upwards, 

 yet its chief effect in the healthy state is 

 exerted in the opposite direction. It is 

 chiefly in disease that an antiperistaltic 

 movement occurs, which conveys bile 

 into the stomach, and even the whole 

 contents of the small and large intes- 

 tine. 



By the powers now explained, which 

 propel the alimentary mass by their con- 

 tractions, and by the admixture of the 

 various fluid menstrua which dilute and 

 alter its properties, those memorable 

 changes are effected, by which our food 

 is said to be animalized or assimilated. 

 In the duodenum and upper part of the 

 jejunum it forms an equably mixed fluid, 

 of the consistence of thick cream, grey- 

 ish, and rather acid. Lower down it se- 

 parates into two parts ; the excremen- 

 titious of a pale brown or yellow colour, 

 and nauseating smell ; and the true chyle, 

 separated from the former by the bile, 

 and swimming- on its surface. 



Jlclion of the large Intestine. The excre- 

 mentitious portion of the chyme, deprived 

 almost entirely of every nutritive portion, 

 enters the caecum : its passage through 

 the last part of the ileum being favoured 

 by a copious secretion of mucous from 

 the glands which abound in that part. 

 The valvula coli, which is the boundary 

 between the large and small intestines, 

 is designed to prevent the contents of the 

 former from regurgitating into the latter : 

 and it performs this office in general ; for 

 nutritive clysters would otherwise enter 

 the small intestines, and thus enable us 

 to administer food enough for the support 

 of life per anum : yet it occasionally 

 fails in its office : hence vomiting of 

 feces, and of tobacco clysters. 



The large intestine may be regarded as 

 the organ in which the residue of the 

 chyme undergoes its last change ; viz. 

 the conversion into feces ; as a reservoir, 

 protecting us from the disgusting neces- 

 sity of having that residue constantly 

 flowing off ; and as the instrument of its 

 final expulsion from the body. 



Some absorbents exist in this last part 

 of the alimentary tube, and convey what 

 nutritive parts still remain in the intesti- 

 nal contents ; but they are comparatively 

 few, and hence the impossibility of nou- 

 rishing the body by way of clyster. 



The conversion of the alimentary resi- 

 due into feces, is owing to some ac- 

 tive operation of the intestine ; as these 

 are very different from the mere putrid 

 remains of animal or vegetable matter. 

 And when this operation is deficient, 

 portions of the food are seen in the eva- 

 cuations per anum, but slightly changed. 

 The fecal matter is conveyed onwards by 

 the peristaltic motion of the large intes- 

 tine : it become thicker and more con- 

 sistent in its progress, and is usually 

 formed more or less decidedly by the 

 cells of the colon. Its natural consist- 

 ence is just sufficient to retain these 

 marks; and its appearance throughout 

 should be homogeneous. The colour de- 

 pends on the admixture of bile, and ia 

 the most natural state is of a yellow 

 brown. Although the change which re- 

 duces the residue of our food to feces, is 

 so far from being mere putrefaction, that 

 the excrement is in fact less prone to pu- 

 trefy than other animal matter ; yet 

 there is, as in putrefaction, a disengage- 

 ment of gaseous products, particularly of 

 sulphurated hydrogen. The colouring 

 matter of the vegetables is often seen in 

 the feces, as the green of spinach, and 

 red of beet root ; and the fibrous indiges- 



