DIGESTION. 



10 



proper state for being received into the duode- 

 num. The undulatory motion of the stomach 

 is more especially effected by the circular fibres, 

 while the longitudinal fibres are more effective 

 in the progressive motion of its contents from 

 the cardia to the pylorus. 



The alimentary mass is now to undergo the 

 last of the three changes to which we referred 

 above, its conversion "from chyme into chyle. 

 These substances are obviously different from 

 each other in their sensible properties, but 

 respecting the exact nature of this difference, 

 the change which they experience, or the mode 

 in which it is produced, we have little certain 

 information. The fact appears to be, that as 

 soon as the uniform pultaceous mass, which 

 composes the chyme, enters the duodenum, 

 it begins to separate into two parts, a white 

 creamy substance, which constitutes the chyle, 

 and a residuary mass, which is gradually con- 

 verted into faeces, and is propelled along the 

 course of the intestine, in order to be finally 

 expelled from the system.* Although no point 

 in physiology appears to be more clearly as- 

 certained than that chyle, properly so called, 

 is never found in the stomach, and that the 

 duodenum is the appropriate organ for its pro- 

 duction, yet owing partly to the inaccurate 

 mode in which the terms have been employed, 

 and partly to the inaccuracy of our obser- 

 vation, some writers, even in our own times,f 

 have spoken of chyle as being formed in the 

 stomach, and have conceived that the only 

 change which was effected in the duodenum 

 was the separation of the chyle from the re- 

 mainder of the mass.J 



With respect to the mode in which this 

 change is brought about, or the agent by which 

 it is effected, we have little to offer except con- 

 jecture. The secretions of the liver and the 

 pancreas are, each of them, conveyed into the 

 duodenum, and it has been stated that the 

 completion of the chyle takes place exactly at 

 the part where the bile and the pancreatic juice 

 enter into the intestines. Of this, however, 

 we do not possess any direct evidence, and 

 the fact, that in certain cases of disease or mal- 

 formation, the process of chylification has gone 

 on, nearly in its ordinary course, although the 

 fluids in question have not been transmitted 

 into the intestine, appears to furnish a de- 



* Prout, ut supra, v. xiii. p. 12 et alibi. The 

 difference between chyme and chyle, as well as the 

 different organs in which they are elaborated, was 

 well known to some of the older writers, although 

 not acknowledged ; see Juncker, Conspect. Physiol. 

 tab. 11 et 25; Vanhelmont, Ortus Med. p. 167, 8, 

 and Baglivi, Diss. 3. circa bilem. 



t Home, in Phil. Trans, for 1807, p. 88, 9. 



t On this subject the reader is referred to the 

 following works : Boerhaave, Praelect. 90 . . 5 ; 

 Haller, ibid, in notis, Prim. Lin. 635 . . 8 et alibi, 

 and El. Phys. xviii. 4. 24, 31 et xxiv. 2. 1 ; Hunter, 

 Anim. CEcon. p. 213 ; Fordyce, ut supra, passim ; 

 Bell's Anut. v. iv. p. 65 et seq. ; Monro's (Tert.) 

 Elem. v. i. p. 552; Richerand, El. Pbysiol. 11, 



<cO. 



The experiments of Sir B. Brodie, in which 

 the formation of chyle appears to have been sus- 

 pended by tying the biliary duct, although inte- 



cisive objection to the hypothesis. Some phy- 

 siologists have conceived that the duodenum 

 itself secretes a specific fluid, analogous to 

 that in the stomach, by which the process of 

 chylification is effected ; but we have no evi- 

 dence of the existence of this fluid, except the 

 supposed necessity to explain the effects that 

 are produced. In this deficiency of direct evi- 

 dence we appear to be reduced to the sup- 

 position, that the conversion of chyme into 

 chyle is effected partly by the mutual action 

 of its constituent elements on each other, aided 

 perhaps, in some degree, by the intervention 

 of the bile and the pancreatic juice.* 



We have various analyses of chyle, which 

 appear to have been made with sufficient accu- 

 racy. It is a white opaque substance, re- 

 sembling cream in its appearance and phy- 

 sical properties. W'hen removed from the 

 body, it shows a tendency to concrete and 

 undergoes a change considerably resembling 

 the coagulation of the blood, by which it se- 

 parates into two parts, a dense white coagulum, 

 and a transparent colourless fluid, analogous 

 respectively to crassamentum and to serum. 

 The chemical properties of chyle appear very 

 similar to those of the blood, and it also re- 

 sembles blood in the nature of its saline con- 

 tents; but it differs from it in containing a 

 portion of oil as one of its essential consti- 

 tuents, while in the blood oil is only an occa- 

 sional, and probably a morbid ingredient.f 



The chemical analysis of chyle was first 

 made by Vauquelin, who employed for this 



Eurpose the contents of the thoracic duct and 

 irge lacteals of a horse. The coagulum from 

 the duct was observed to be of a light pink 

 colour, while the corresponding part from the 

 lacteals was nearly white ; but it is not ascer- 

 tained how far this difference of colour de- 

 pended upon an accidental occurrence, or 

 whether it is to be regarded as a uniform cir- 

 . cumstance. The coagulum contained a sub- 

 stance which bore a considerable resemblance 

 to fi brine, or perhaps more correctly possessed 

 properties intermediate between fibrine and 

 albumen. The liquid part of the chyle was 

 found to be very similar to the serum of the 

 blood, differing from it only in containing a 

 quantity of an oily or fatty substance; like 

 serum it exhibited marks of an uncombined 

 alcali.J 



resting and important, cannot be regarded as con- 

 clusive, until we are more minutely informed of 

 every circumstance connected with them; Quart. 

 Journ. v. xiv. p. 341 et seq. 



* Dr. Prout conceives, that the bile is the prin- 

 cipal agent in this process ; and that when it is 

 added to the contents of the duodenum, it separates 

 the chyle by a kind of precipitation ; it does not, 

 however, appear very clearly what is the exact 

 nature of the chemical action which takes place. 



t Fordyce, p. 121 ; Young's Med. Lit. p. 516 ; 

 Dumas, t. i. p. 379 . . 1 ; Magendie, t. ii. p.154.,8. 

 Some late experiments appear indeed to prove that 

 a certain quantity of an oily matter is always present 

 in the blood ; but the proportion in the chyle is at 

 least very much more considerable. 



$ Ann. Chim. t. Ixxxi. p. 113 et seq.; Ann. Phil, 

 v. ii. p. 220 et seq. We have some experiments 

 on chyle by Enamert, previous to those of Vauque- 



c 2 



