144 THE STRUCTURE OF THE HORSE. 



Thus, an organ which, when only known in one 

 animal, appeared strange, anomalous, and puzzling, 

 because there seemed nothing to account for its 

 presence, acquires in the light of wider knowledge a 

 much deeper interest ; for if we cannot yet discover 

 its purpose, its existence in some modification in all 

 of these three very distinct forms, and in, as far as 

 is known, no other mammal, is a strong corrobora- 

 tion of the view, formed upon other evidence, of their 

 close affinity and common descent. 



In the ass, the pouch is said to be deeper than in 

 the horse, and areolated at the blind extremity j but 

 detailed comparative observations upon its condition 

 in the different species of existing Equidce and upon 

 its development in the horse are almost entirely 

 wanting, and would well repay the trouble the inves- 

 tigation would cost. The nearest analogue in other 

 orders of mammals is perhaps the singular pouch 

 developed from the upper part of the commencement 

 of the nasal passage of the "bladder-nosed" seal 

 (Cystopliora cristata), which the animal has the power 

 of inflating with air when excited. The analogy is, 

 however, by no means close, as in the seal the pouch 

 is only found in the male, and not even in the young 

 of that sex. If the sac in the horse is the remnant 

 of some organ which formerly played a more im- 

 portant part in the economy of the race, we should 



