478 DIGESTION IN HERBIVORA. [BOOK II. 



The rapid passage of the solid gastric contents of the horse into 

 the intestine has been determined both by Tiedemann and Gmelin 

 and by Colin ; these observers having administered foreign bodies to 

 horses found them (unless their size was too great) in the intestine 

 an hour or an hour and a-half afterwards. It is by the short contact 

 with the gastric juice that Colin explains the fact that pieces of 

 meat, oysters, &c., administered to horses are usually found to pass 

 undigested into the intestine. 



Amongst the phenomena connected with the alimentary canal of 

 the horse which deserve to be mentioned, is the remarkable rapidity 

 with which water passes out of the stomach in this animal and 

 is conveyed towards and into the immensely capacious caecum, 

 where the absorption of water, and probably of soluble products of 

 digestion, appears to have its chief seat. By adding ferrocyanide of 

 potassium to the water drunk by horses, Colin found it in ten 

 minutes in the ileum, at a distance of 20 metres from the stomach, 

 though a somewhat longer time was needed before it entered the 

 caecum. To the processes which have their seat in the caecum of 

 the solidungula we shall refer when discussing the changes which 

 cellulose undergoes in the alimentary canal of the Herbivora gene- 

 rally. 



' The stomach of ruminants, such as the ox, sheep, goat, 

 of R eS in m t C deer, chamois, elk, camel, dromedary, giraffe, &c con- 

 sists of four sacs (a) the paunch or rumen, (b) the reticu- 

 lum, (c) the psalterium or omasum, and (d) the abomasum or true stomach. 

 The paunch is a sac of enormous capacity, in the ox capable of containing 

 100 litres, and in the sheep 4 to 6 litres. The mucous membrane is 

 covered with pointed papillae from 3 to 9 mm. in length, and the epithelial 

 layer is of the stratified squamous variety. The paunch communicates 

 with the lower end of the oesophagus and also with the reticulum. The 

 paunch and reticulum are divided by a constriction and strong band of 



fibres from the psalterium and abomasum The reticulum has a 



capacity in the ox of 2 litres, and in the sheep of 0*2 litre. It shews, as 

 its name indicates, a honeycomblike appearance, or reticulum, each cell of 

 which is polyhedral. The height of the walls of these cavities may be 

 from 10 to 15 mm. Its muscular coat is stronger than that of the paunch, 

 and consists mainly of striated muscle, the fibres of which are continuous 

 with those of the oesophagus. The walls of the reticular spaces also con- 

 tain muscular fibres. The wall of the reticulum can thus contract more 

 powerfully and speedily than that of the paunch. Fine papillae abound, 

 and the whole mucous membrane is covered with stratified squamous epi- 

 thelium. The reticulum has three openings a large one towards the 

 paunch, a narrower one towards the psalterium, and a third which com- 

 municates with the oesophagus. At the opening into the psalterium, we 

 find a sphincter surrounding an aperture narrowed by rugae or folds, or by 

 papillae, so that matters entering into the psalterium from the reticulum 

 pass through a kind of 'perforated partition.' The psalterium or omasum 

 has a thin wall, and has two openings, one into the reticulum, already 

 alluded to, and the others in the true stomach or abomasum. The mucous 



