FOSSIL ANCESTOES OF THE HORSE 509 



the internal ear, called the Eustachian tube. The guttural pouches do 

 not now appear to have any special function, and to the veterinary surgeon 

 they are a source of anxiety in many cases, as they are liable to become 

 diseased from the lodgment of foreign substances in them. Sometimes 

 they are the seats of purulent deposits, and now and then become dis- 

 tended with air. 



Altogether, so far as the horse of domestication is concerned, they 

 might apparently be dispensed with, notwithstanding their value as relics 

 of a long-past order of things. 



FOSSIL ANCESTORS OF THE HORSE 



The preceding remarks on the special characters of some portions of the 

 horse's structure, and on the presence of organs and parts which have now 

 no obvious use or function, have cleared the way for a brief enquiry into 

 the evolution of the horse. Organs which are now gradually becoming 

 rudimentary and useless must have once formed essential parts of the 

 animal's structure; and in their present state it may be said of them that 

 their existence cannot be satisfactorily accounted for except on the assump- 

 tion that they were transmitted from remote ancestors in gradually modified 

 forms, becoming less and less definite in character as they became either 

 obstructive or unnecessary to the animal in its different surroundings audi 

 new mode of life. 



The doctrine of evolution has already been illustrated by reference to 

 the process of generation in the higher and lower forms of life. Changes 

 in the small mass of " undifferentiated (that is, formless and jelly-like) 

 protoplasm " in the human ovum (egg) have been seen to result in the 

 development of a mature human form; and almost identical changes in a 

 microscopic cell in the ovum of other animals have also been referred to. 



No hesitation is permissible in respect to the facts of evolution which 

 have been described. Wonderful in truth they are, unbelievable, perhaps, 

 to many, but nevertheless commonplace facts to the man of science, who has 

 had the faculty of wonder obscured and dimmed by incessant repetition of 

 the marvellous in his daily work, and who can no longer take refuge in 

 doubt, because the evidence forces him altogether out of the region of 

 doubt. 



Continuing the investigation in the direction of the previous remarks, 

 evidence has now to be produced from the discoveries of geology to justify 

 the assertion that the modern horse had its origin in the remote past in 

 ancestors the history of which can be traced from the earliest beds of the 

 Tertiary formation up to deposits of a comparatively recent date. 



Vol. III. 98 



