INTRODUCTION. Ixvli 



" that the structure of the teeth, as manifested by means of the 

 microscope, forms a new, distinct, and specific guide for classifying 

 the different members of the animal kingdom, and determining their 

 respective types :"(1) the absurdity of which will be obvious to the 

 youngest student of Zoology, who knows that true teeth are developed 

 only in one of the primary divisions of the animal kingdom. What 

 I have stated is, that the teeth, by their microscopic structure, as 

 well as their more obvious characters, form important, if not 

 essential aids to the classification of existing, and the determination 

 of extinct species of Vertebrated animals : but in this compara- 

 tively restricted sphere the teeth have different degrees of value, 

 as zoological characters, in different classes ; the lowest degree 

 being in the Class of Fishes, and the highest in that of 

 Mammals. Numerous rows of teeth, for example, gradually suc- 

 ceeding and displacing each other, characterise the higher organized 

 or Plagiostomous Fishes, and particular modifications of the form and 



(I) " The labours of Purkinje, MuUer, and Retzius on the structure of the teeth have now 

 been recorded, and the views entertained by these physiologists have been most ably investi- 

 gated and confirmed by Mr. Owen, who has submitted to microscopical examination the 

 teeth of several other animals, both recent and fossil. From an excellent Report of these 

 Researches read at the last Meeting of the British Association, I have great satisfaction 

 in finding that he has arrived at the same conclusion which I had previously embodied in 

 the first announcement of this work, viz., that the structure of the teeth, as manifested by 

 means of the microscope, forms a new, distinct, and specific guide for classifying the different 

 members of the animal kingdom, and determining their respective types. From the enduring 

 nature of these organs, the characteristic modifications which they present, will form, as Mr. 

 Owen has admirably pointed out, a most valuable accession to geological science." — Mr. 

 Nasmyth, 'Researches on the Teeth,' 8vo. 1839, p. 123. Where this Author obtained the 

 idea, "which he had previously embodied" to the best of his comprehension, is of little 

 moment. The paragraph is cited to show that when Mr. Nasmyth penned and printed his 

 eulogy on my " Report" of 1838, he seemed not to feel it as " a strange and unlooked for 

 opposition" as he has represented it since the exposure, in 1840, of the nature of his ' Papers' 

 read at Birmingham. 



