XIV PREFACE. 



much of what is now regarded as established truth, will need great 

 modification to be brought into accordance with the results of new 

 inquiries. It is very desirable, therefore, that the Student should not 

 be made to think so confidently of his acquirements as to be indisposed 

 to receive new information, even though it should tend to diminish their 

 value. 



The present Treatise is to be regarded as complete in itself, and as 

 quite independent of the Author's "Principles of General and Compara- 

 tive Physiology." That it may be so, he has inserted an introductory 

 chapter on the "Place of Man in the Scale of Being," and numerous 

 references to the Comparative Physiology of the lower Animals. Still 

 he does not hesitate to express the opinion that, the greater the amount 

 of the Student's previous general knowledge of the Science, the better 

 will he be prepared to enter upon any department of it, especially that 

 peculiarly complex and difficult branch, the Physiology of Man. On 

 every topic it has been the Author's aim to present the latest and most 

 satisfactory information within his reach ; and he believes that the 

 Volume contains much that will be new to the Physiologist, whose 

 reading has not been tolerably extensive. Its materials have been but 

 little derived from other Systematic Treatises on the subject; and it will 

 not be found to bear, as a whole, any considerable resemblance to those 

 already before the public. The Author has rather endeavoured to bring 

 together the valuable facts and principles, scattered through the best of 

 the numerous Monographs that have been recently published on special 

 divisions of Physiology and Medicine; and to reduce these disjecta 

 membra to that systematic form, which they can only be rightly made to 

 assume, when brought into relation with" each other, and shown to be 

 subservient to principles of still higher generality. In regard to this, 

 as to his former Treatise, the Author believes that he may claim a 

 somewhat higher character than that of the mere Compiler ; and that 

 even the well-read Physiologist will find in it many facts and deductions 

 which have not been previously brought before him in the same form. 



In apportioning the amount of space to be devoted to each division 

 of the subject, the Author has had in view its practical relations, much 

 more than its merely scientific interest; and he has on this account 

 bestowed a much larger share on the Organs of Animal life than some 

 may think just, when compared with the narrow limits within which 

 other important topics are discussed. But he has endeavoured to keep 

 always in view, that he is writing for the guidance of the Student who 

 is to become a Practitioner, rather than for him who makes the pursuit 

 of Science his professed object; and that much that is of the highest 

 interest to the latter, is comparatively valueless to the former. Hence 



