PEEFACE TO THE SIXTH EDITION, 



IN the preparation of a new edition of Dr. Kirkes's Hand- 

 book of Physiology, it seemed to me that one of two 

 courses must be pursued either, on the one hand, simply 

 to add to the book such new theories or facts as may have 

 been recorded since the publication of the last edition ; or, 

 on the other, without disregarding work in physiology 

 that may have been lately done, thoroughly to revise the 

 whole work as a hand-book for students, and to regard 

 the discussion of all new and crude matter as secondary in 

 importance to a clear enunciation of those grander facts on 

 which alone all true knowledge of the science must be 

 founded. 



Taking into consideration the position held by the book 

 as one especially for the use of students, there seemed to 

 be no doubt that the latter was the right course ; and I 

 have, therefore, as rigidly as was possible, abstained from 

 inserting all contradictory statements, raw theories, and 

 descriptions of imperfectly or ill-observed facts. A con- 

 stant production of these is of course unavoidable, and 

 indeed necessary for the progress of such a science as 

 physiology, the growth of which can be effected, like 

 that of the beings with whose life it deals, only by gradual 

 assimilation of crude matter, with ceaseless displacement 

 and reconstruction. With the manner of growth, how- 

 ever, of the science, the student has little to do ; he has 

 but to consider the result as it is in his time ; and with 

 this idea in view, I have, although very diffidently, altered 

 such portions of the last edition of this work as appeared 

 to me to fail, either by the unnecessary recital of contra- 



