MOVEMENTS OF THE STOMACH. 141 



Saline aperients, if given in a sufficient state of concentration, probably act 

 chiefly by producing eudosmosis ; but partly also by causing increased secre- 

 tion, not by increasing peristalsis. 1 Certain poisons excite lively intestinal 

 movements. Nasse observed that injection of uicotin and of sulphocyauide 

 of potassium caused violent tetanic spasms of the small intestines in rabbits. 

 Opium acted but slightly, and strychnia and woorara were totally inoper- 

 ative. Carbonic acid intoxication caused general contraction, but no active 

 movements of the walls of the intestines. 



98. The rapidity with which the food traverses the intestinal tube is sub- 

 ject to great variations. In a case of duodenal fistula in a man, recorded 

 by Kiihne, 2 portions of uncoagulated milk, and small fragments of meat, were 

 observed to make their appearance within ten minutes of their being swal- 

 lowed. In a case of artificial anus which opened into the upper part of the 

 jejunum, reported by Dr. Busch, 3 the first portions of food usually appeared 

 in from fifteen to thirty minutes after ingestion. Whilst in another case 

 reported by Dr. Brauue, 4 in which the artificial anus communicated with the 

 intestine a few inches above the ileo-colic valve, the first appearance of the 

 food presented itself three hours after iugestion, and the last about six hours 

 after, so that we may consider the time occupied by the food in traversing 

 the small intestine, to be about 2i hours. The food having traversed the 

 small intestine, enters the csecum by an aperture guarded by a valve (the 

 Ileo-crecal), whose lateral position is clearly a provision for preventing the 

 whole weight of the Faeces, as the remains of the food here begin to be called, 

 by which it might be forced back, from resting upon it. The Faces, in their 

 ascent, are lodged in the sacculi of the colon, by which they are supported 

 during the intervals of the peristaltic action of the Muscular Coat. In their 

 course through the descending colon, they pass through its remarkable sig- 

 moid flexure, by which they are prevented from directly pressing against the 

 anal orifice. 5 According to the observations of M. Voit, 6 in cats and dogs 

 the evacuation of fteces, known by their characters to proceed from particu- 

 lar kinds of food previously given, almost invariably occupies 24 hours. 



99. On examining the outlet by which the feces are voided, we find that 

 it is placed, like the entrance, under the guardianship of a ganglionic centre 

 described by Masius, termed the auo-spinal centre, situate in the lower part 

 (opposite the sixth lumbar vertebra in the Rabbit) of the Spinal Cord ; sub- 

 ject, however, to some control on the part of the will. In the lowest animals, 

 the act of discharging excrernentitious matter is probably as involuntary as 

 are the acts immediately concerned in the introduction of nutriment ; and 

 it is performed as often as there is anything to be got rid of. In the higher 

 classes, however, such discharges are much less frequent, and reservoirs are 

 provided, in which the excrementitious matter may accumulate in the inter- 

 vals. The associated movements required to empty these are completely 

 involuntary in their character, and are excited by the quantity, or stimulat- 

 ing quality, of the contents of the reservoir. But, had volition no control 



1 Legros and Onimus, op cit. 2 Physiologische Chemie, 1868, p. 53. 



3 Virchow's Archiv, vol. xiv, p. 140. 4 Archives Generales de Med., 1861, p. 610. 



5 For some further observations on Defecation, the reader is referred to O'Beirne, 

 New Views of the Process of Defecation, Washington, 1834; and to vol. ii, p. 406, 

 of Dr. Austin Flint's Physiology of Man, both of whom agree in believing that un- 

 der ordinary circumstances the roctum is contracted, and contains neither fjeces nor 

 gas, whilst the condition which immediately precedes the desire for defecation is 

 probably the descent of the contents of the sigmoid flexure of the colon into the 

 rectum. They admit, however, that under certain circumstances fteces must accumu- 

 late in the lower and dilated portion of the rectum. 



6 Zeits. f. Biologic, Bd. ii, p. 6. 



