ORGANS OF CIRCULATION AND RESPIRATION. 45 



true that we are able to ascertain experimentally that, certain 

 parts being gone, certain functions are destroyed, and that, by 

 slicing off consecutive portions of the brain, certain faculties 

 disappear ; but of the ultimate essence of the nervous action we 

 know much less than we do of the electrical phenomena which 

 attend upon the action of the telegraph. However, to understand 

 the effect of medicines as far as is known, and the cure of diseases, 

 thus much of the nervous system is all that is necessary. Here, 

 as in all other organs, size is power the large brain will give 

 increased intelligence, or increased appetites, according to the 

 part which is developed and in proportion to the tone of the 

 nervous system will be the activity and liveliness of the individual. 

 ORGANS OF CIRCULATION AND EESPIRATION. The bones, muscles, 

 and nervous system, indeed, every part of the body, must be 

 supplied with blood, and with warm blood, too, in order to the 

 performance of the action which each part has to fulfil. Bones 

 must be nourished, muscles must be nourished also, and be 

 supplied with arterial blood before they can act, as must the brain 

 and nervous system generally. All these organs are built up out 

 of the blood at the time when it is circulating in the minutest 

 arteries, which are termed the capillaries. The stronger and 

 quicker the contraction of the muscles, and the more vigorous the 

 action of the brain, so much the faster must the blood be furnished 

 by the agency of the heart. Hence, it has become a general 

 observation that a dog or horse which fails in his effort ' has a bad 

 heart,' and so he often has. A weak heart is totally incapable of 

 carrying on the circulation under distress, but becomes clogged, 



