308 



THE CAUSES OF THE 



XT 



reduce this notion of a horse that we now have, to 

 some such kind of simple expressions as can be at 

 once, and without difficulty, retained in the mind, 

 apart from all minor details. If I make a trans 

 verse section, that is, if I were to saw a dead 

 horse across, I should find that, if I left out the 

 details, and supposing 1 took my section through 

 the anterior region, and through the fore-limbs, I 

 should have here this kind of section of the body 

 (Fig. 1). Here would be the upper part of the 



animal that great 

 mass of bones that 

 we spoke of as the 

 spine (a, Fig. 1). 

 Here I should have 

 the alimentary 



canal (b, Fig. 1). 

 Here I should have 

 the heart (c, Fig. 

 1) ; and then you 

 see, there would be 

 a kind of double 

 tube, the whole 

 being inclosed with 

 in the hide ; the spinal marrow would be placed 

 in the upper tube (a, Fig. 1), and in the lower 

 tube (d d, Fig. 1), there would be the alimentary 

 canal (b), and the heart (c) ; and here I shall 

 have the legs proceeding from each side. For 

 simplicity s sake, I represent them merely as 



Fig. i. 



