INTRODUCTION. 



" BY the classification of any series of objects, is meant the 

 actual or ideal arrangement together of those which are 

 like, and the separation of those which are unlike ; the pur- 

 pose of this arrangement being to facilitate the operations 

 of the mind in clearly conceiving and retaining in the me- 

 mory the characters of the objects in question " *. 



In the animal and vegetable kingdoms there is a mar- 

 vellous interconnexion of organisms, perhaps genetic in its 

 origin, which enables us to classify them into groups based 

 upon purely structural considerations. Such a classifica- 

 tion has been well termed " morphological." 



Amongst malformations there is no such interconnexion. 

 Parts of organisms which have no morphological relation 

 with each other are affected by causes which are very dif- 

 ferent in their nature and working. In such cases we must 

 not seek for a morphological classification ; we have to deal 

 with phenomena which may or may not be connected with 

 or dependent on each other, and the only satisfactory method 

 of arrangement must be physiological. 



The classification of malformations on these principles, 

 to be entirely satisfactory, would require an intimate ac- 

 quaintance with the laws of abnormal development, and the 

 causes producing deviations from the normal standard. At 



* Huxley, ' Lectures on the Elements of Comparative Anatomy,' p. 1. 



