294 STRUCTURE OF THE SHEEP. 



These nerves proceed either from the brain or spinal cord, 

 which, therefore, may be considered as the fountain of sen- 

 sation and the residence of the mind. And thus sensation 

 is first sent from the extremities to the brain by the nerves, 

 and then by another set of nerves the will is conveyed to 

 the muscles. 



The hraiii is a soft pulpy substance contained within the 

 head, and the spinal cord is somewhat similar in structure, 

 and extends from the brain to the tail, through a hole in the 

 bones which form the spinal column. The body is divided 

 into two principal cavities, the chest and the abdomen, and 

 separated by a muscular partition called the diaphragm. The 

 former contains the heart and lungs, whose uses are princi- 

 pally to purify and distribute the blood by means of the res- 

 piration and the circulation ; and the latter contains the stom- 

 ach and bowels, in which the functions of digestion are car- 

 ried on, besides several important glands, such as the liver, 

 kidney, and pancreas, together with other supplementary 

 parts. Both the small and large intestines are fastened to 

 the spine by means of a strong membrane called the mesen- 

 tery, which, besides veins and arteries, is furnished with a 

 vast number of small vessels called lacteals. These lacteals 

 open into the intestines, and there absorb the nutritious part 

 of the food, which is a white milky fluid called the chyle, 

 and convey it to a vessel running along the course of the 

 spine, which empties itself near the heart into the circulating 

 system. Thus by these means the blood becomes enriched 

 with nutriment, and is thus enabled to supply the constant 

 waste the system is continually undergoing. 



The blood being furnished with nutriment, requires to be 

 purified before it is fit for circulation ; for this purpose it 

 passes into the right side of the heart, by the muscular con- 

 traction of which it is sent to the lungs, where- it becomes 

 exposed to the action of the atmosphere, by which it is 

 changed from a dark to a light red color, and being freed 

 from impurities, it enters the left side of the heart, and from 

 thence is sent, by means of the arteries, to all parts of the 

 body, supplying every part with nourishment, and furnishing 

 the various glands of the body, not only with their own 

 proper nourishment, but with material for the secretion of 

 their peculiar fluids. Thus the salivary glands separate the 

 saliva from the blood ; the pancreas, a juice somewhat sim- 

 ilar ; the testicles, the semen ; and the kidneys, the urine. 



