817 



'I'll.- peiistalsis in the stomach ia combined l.y 

 irregular churning moxements. 



Tin- act of \. uniting is a re!le\ neixoiiMact. It 



c.iii l>e excited liy stimulating tin- branches of tlic 



\e, \\llii-ll lllf distributed (i, (he -|,iiii;irli. 



-tihle ami irritative food i> taken ; or 

 mi-tics. such as luii.stunl, hot water, or u hot 

 solution, tartar emetic, ipecacuanha, sulphate 

 of /.inc. ami ilium art- administered. My tickling 

 tin- Lack of the throat \\ith a tVathrr, tin- glos>o 

 phsjyagea] nerxe i- stimulated, ami vomiting max 

 rt-adily I > produced. It in of frequent occurrence 

 xx hen painful irritation of tin- utei im- nerves in preg- 

 nancy, of the nerves of the liver ami kidney* during 

 the passage of a hepatic or 

 renal stone, or indeed when 

 irritation of any .-i-n-mx 

 nerves taken place. Nnvi- 

 impulse- max pass to the 

 brain through any one of 

 these channels (tig. 10), or 

 may lie excited in the brain 

 itself by the sight or smell 

 or even the thought of any- 

 thing disgusting, and they 

 produce, if the person be con- 

 scious, a feeling of nausea. 

 .In any case there is a dis- 

 charge of nerve-impulses, 

 which, as a result of this 

 stimulation, passes to the 

 glands of the mouth through 

 the chorda tympani nerve, 

 and produces a rapid flow 

 of saliva. In addition, motor 

 nerves carry impulses to the 

 muscular walls of the ab- 

 domen, and to the walls of 

 the stomach itself. As a 

 result of the muscular con- 

 traction which follows, the 

 conti-nts of the stomach are 



Fig. 10. Sensory 

 Net 



, 

 P, lungs L, pill-bladder 



B. 



Serves concerned in 

 Vomiting : 



Nerves come to vomiting 

 centre V, through apiiial 



cord SC, from pharynx propelled upwards into the 

 mouth. Just In-fore vomit- 

 ing an inspiration generally 

 occurs, and the aperture of 

 the larynx (glottis) is closed. 

 The diaphragm the muscle which separates the 

 thorax from the abdomen then becomes preened 

 down upon the abdominal contents, and assists in 

 the act of vomiting. Cases in which irritating or 

 poisonous sulmtances are swallowed are so frequent, 

 that every one should be aware that a large quan- 

 tity of hot liquid, especially if it contain much salt, 

 or some mustard, forms a safe and speedy emetic. 

 Ice is a valuable sedative, and often prevents 

 vomiting. The undigested food when it reaches 

 the lower part of the intestine (rectum), excites 

 sensory nerves which carry impulses to the brain 

 and spinal cord. A feeling of distension results, 

 and voluntary contraction or the abdominal muscles 

 and of the diaphragm an inspiration usually 

 taking place expels tne undigested matter. This 

 voluntary effort is aided by the contraction of the 

 bowel itself, and by the relaxation of the band of 

 muscular fibres (sphincters) which, during the in- 

 tervals Ixjtween evacuations, remain contracted. 



In many animals, such as the sheep, ox, and 

 camel, the stomach consists of several cavities com- 

 municating with one another. In the ox and sheep 

 both the cardiac and the pyloric portions are each 

 subdivided into two compartments. The cardiac 

 part consists of a very dilated cavity, the paunch 

 (rumen), into which the food is pa-ssed as soon as 

 swallowed. In addition there is a smaller part, the 

 reticulum (honeycomb), so called from the folds of 

 lining mucous membrane which intersect, forming 

 a reticulum. The pyloric half is divided into two 

 156 



part*. The p-.alt.-ii. m, ( multiplies), so called from 

 the lain. -Hat.-. I iipjx-arance of n- IM'IHU (petnbrtne, 

 communicate* with tin- U-t OIXIMOII, the rennet 



-tima.-li ahoma>um. Jig. II). 



l-'lni.l passes either into the first, Meond, or third 

 partH of the stomach, ami tln-m-eon into the fourth 

 Solid matter, -n< h .1- ^nt--, root-. ,\ < , poMMS either 

 into the paunch or reticulum. This i n,i\.-<l with 

 tin- saliva sxvalloxxcd with it, and in addition 

 mixed with juice* formed by the mucoii- -. 

 of these cavities. \\ h.-n the animal ha* finished 

 feeding, it lies down and rumination commence*. 

 Dm- in part to the contraction of the al-l-.minal 

 muscles and diaphragm, tin- food '* profiled in the 

 form of rounded pellets from the paiim-h and n-ti 

 culiim up into the mouth. The |-llets are there 

 thoroughly masticated, and are returned in a pulpx 

 condition to the stomach. Noxv, however, the food 

 passes into the psalterium, and finally into the 

 rennet stomach. It will be seen, therefore, that 

 the consistency of the food determines into which 

 part of the stomach it posses. The walls of the 

 stomach near the gullet are thrown into two folds 



Fig 1L Compound 



Stomach of Ox : 

 a, oesophagus; b, rumen, or 

 paunch ; r, n-ticuluin, or 

 second stomach ; tl, omasum, 

 or third stomach ; , abom- 

 asum, or fourth stomach ; 

 /, the duodenum. 



Fig. 12. Alimentary 



Canal of Fowl : 

 i, oeaophagtw ; 6, crop; c, pro. 

 ventriculus. or secreting 

 stomach ; </, giuard, or tri- 

 turating stomach; . Into*. 

 tinol canal: /, two lone 

 CKcal tubes indicating UM 

 theoretical i unauneMsjt 

 of large int*tine. 



or lips which, when in contact, form a tube leading 

 from the gullet into the i>salterium. Along thi* 

 tube the masticated and fluid food can pan. The 

 mouthfulsof gross which are first swallowed pass 

 between their lips, and find their way at once into 

 the paunch or reticulum. 



In the bird some interesting modifications in the 

 structure of the alimentary canal are Keen (fig. 12). 

 The gullet at about the middle of it* coarse to pro- 

 vided with a jMMich or crop. Into this the food 

 passes, and is bathed by a secretion formed ' l 

 glands. It is then propelled onward" into a di 

 cavitv. the proventriculus. and U acU^I on bv diges- 

 t ix e juices. Thence it pos.se* into the gizzard. This 

 cavity is provided with muscular wall* of enormous 

 thickness in the case of birds that are vegetable- 

 feeders. It is lined by thick and corneous epithe- 

 lium, and in its interior are generally found pieces 

 of -tone, chalk. Arc. The gizzard is a powerful 

 mill, which grinds the food into a soft pulp, upon 

 which the digestive juices can readily act (see 

 BIRO). 



