INTRODUCTION. 3 



The extent to which variation in normal anatomy is an exciting 

 cause of disease is difficult to determine. All things remaining the 

 same, it may be said that the most variable parts are seen in the 

 regions which are in extremes of specialization, as in the nasal 

 chambers of man, and that these chambers are degenerate as com" 

 pared to many mammals where tlie i-ange of variation is small. 

 The pre-disposition of nasal disease in man cannot be rationally dis- 

 associated from the proneness of the parts which enter into the com- 

 position of the nose to vary. If this statement can be depended 

 upon, the publication of all details of structure in the nasal cham- 

 ber becomes essential. 



This essay is a contribution to the morphological study of dis- 

 eased action. The writer trusts that increasing interest may be 

 awakened in the proposition that medicine for the most part is a 

 science based on biology. The study of biology should not be the 

 preparatory work of the trio only, but should be the subject of un- 

 ceasing assiduity in every phase of medical research. The study of 

 anatomical variation in the human frame is a phase of biology, and 

 it is held in this connection to be a subject as important as any other 

 which may claim the attention of the student of etiology of disease. 



The materials upon which the essay is based were found in the 

 collections of the Academy of Natural Sciences of Philadelphia and 

 of the College of Physicians of Philadelphia. The letter C, in 

 absence of other signs, will indicate that a specimen so named is to 

 be found in the College of Physicians (Hyrtl Collection); the re- 

 mainder are in the Academy. (The last named are often indicated 

 by the letters A. N. S.) 



The determination of percentage of frequency of any anatomical 

 peculiarities has not been attempted. The writer has been con- 

 tent to give the numbers and nationalities of the specimens re- 

 ferred to. 



The entire number of specimens of crania in the Academy is 

 1,750, and in the College of Physicians 156. 



