vi PREFACE TO THE SECOND EDITION. 



also written the chapter on Comparative Physiology. To 

 my assistant, Mr. R. A. Staig, I am indebted for the index. 

 I wish to express my thanks to my artist friend, Mr. 

 William Smith, for the carefulness with which he has 

 executed many of the illustrations ; and I am indebted 

 to Dr. Traquair for allowing me to figure some of the 

 specimens in the Edinburgh Museum of Science and 

 Art. In regard to these illustrations, I may say that in 

 almost every case they have either been derived from 

 original memoirs and works of reference, or drawn from 

 specimens. Of course, no one who has worked with such 

 excellent practical books as that by Marshall and Hurst 

 or Parker's Zootomy, can help being assisted by them in 

 preparing analogous diagrams ; but I have refrained from 

 incurring any but an absolutely necessary debt to such 

 books, except in the case of Figure 215, which Messrs. 

 Macmillan have kindly permitted me to make use of. 



J. A. T. 



School of Medicine, 



Edinburgh, March 1895. 



