SYSTEMATIC ANALYSIS OF MEMBERS. 53 



115. IT is EVIDENT that parts of the mental group 

 must be double ; a person could not walk without two 

 lower extremities, and all the parts that control them, 

 the nerves and parts of the brain inclusive, must be 

 double. So also it must be with the upper extremities. 

 All will allow that there should be two ears and two eyes 

 for the purpose of hearing and seeing well; but the same 

 persons will not as readily notice that there are two 

 noses, because they are near together, and are spoken of 

 as single, while practically each nostril' is a nose. In 

 fact, all the mental class of organs are, and of right ought 

 to be, double ; and the seeming exceptions confirming the 

 rule will be accounted for under synthetic details. 



Fig. 71 represents a section FIG. 71.^^^^^ '^^^^ss^^sss^ 



across the neck, to illustrate 

 the double and single charac- 

 ter of parts belonging to the 

 two groups. 11, 12, 13, the 

 Thyroid Gland, Windpipe 

 or Trachea, and (Esophagus 

 or meat-pipe, are single, and 

 belong to the 2d group ; all 

 the other numbers belong to 

 the 1st group, are double, and 

 are muscles, except 14, Blood- 

 tubes ; 28, vertebrae; sc, spi- 

 nal canal. 



116. IT MAY APPEAR that some of the contents of 

 the Trunk are double ; they are not, properly speaking. 

 The Lungs are called right and left, and so are the kid- 

 neys ; but both of each are required to effect their func- 

 tions, and the whole blood and body suffers if either is 

 deficient in its duties. Anatomically they may be spoken 

 of as double, but Physiologically they are considered as 

 single and composed of two halves. It is not so with the 

 organs of the first group ; one eye does not enlarge when 

 the other is diseased, as one lung sometimes does, nor 

 will the ear enlarge as one kidney will. Each lung and 



115. What is ? Describe Fig. 71. 116. What ? What organs in the Trunk- 

 walls are spoken of as double ? How are they Physiologically ? 



